Windows XP/2003 and earlier (can't attest to Windows Vista, but I suspect it's the same) all appear to become more sluggish over time as applications are installed and uninstalled.

This is not a scientifically tested observation, but more of a learned-through-experience piece of wisdom. (I've always suspected the registry as being behind the issue.)

Is there any concrete evidence of this degradation occurring, or it just an invalid perception of mine?

  • 1
    What is your timeframe? I assumed over months, others are assuming shorter.
    – StingyJack
    Nov 20 '08 at 16:09
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    My experience with vista is that it hasn't actually slowed down over time. I'm sitting on an 18 month install, and it's still just as slow as it was when I first installed it! Nov 20 '08 at 20:13
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    @MusiGenesis - It's a big problem for all people not just developers. You're starting down a slippery slope. This isn't a programming related question any more than the car you drive being related to programming. It gets you to your job, but that's about it. Nov 21 '08 at 12:29
  • 2
    Should be moved to superuser.com, because it is not only relevant for programmers.
    – Mnementh
    Apr 7 '10 at 10:42
  • 1
    I'm tempted to answer this question with one word - Adobe (things like Reader_sl.exe etc).
    – Dan Diplo
    Apr 7 '10 at 10:43

23 Answers 23


I don't know what it is with the others here, I haven't met someone that doesn't know what you are talking about. There are many reasons for it, but some have not been identified.

I'll start with a better description for those that don't know. A fresh install of Windows will boot in under 1min. Over a period of 6 months the computer's boot time will not only slow but the entire experience of the OS is not on par with a clean slate. If you ever reinstall windows after 1 year of use you are sure to see the difference.

Reasons for the slow down have been attributed to increased clutter in your registry, and fragmentation of your disk. You have noticed that uninstalling does not help, this is in part because everything isn't cleaned from the registry. Ad-ware can be an issue, but this is usually not the cause.

You can get registry cleaners, defreg, and remove ad-ware, but even this will not return the system to its original speed, no one has come up with a reasonable explanation for this, it just is.

Note to others, this is not a normal behavior for an OS that is being used, I have been using Linux for 4 years, while this wasn't without re-installation, there had never been performance increase from a re-install or a slowdown from large amounts of installing/uninstalling programs.

  • 1
    My other guess is that it might be due to the Windows Update process and how it patches. That's complete conjecture on my part, derived from the standpoint that I've seen this behavior on machines that only surf the web and get Windows Updates.
    – webjedi
    Nov 20 '08 at 16:37
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    Fragmentation isn't a large speed issue as long as you aren't using FAT32 any more.
    – tloach
    Nov 20 '08 at 16:44
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    @webjed, I do know that doing a Windows update from a fresh install does not have this effect, but I wouldn't be surprised if progressive updates would cause this issue. Nov 20 '08 at 16:45
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    To make the test fair, you need to install all the software and updates on the new system. A base, fresh install of Windows does nothing, but does it very fast. An interesting test would be to have a registry probe application and test performance changes with it.
    – Mr Fooz
    Nov 20 '08 at 16:50
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    Registry access is an O(n) operation where n is the depth of the tree. Having a huge registry with lots of clutter will not cause performance problems. However, there are two things that are related to the registry that do slow things down. The first is fragmentation of the registry hive files. The second, and heavier impact of the two, is that applications will register callbacks and addons and modules to be loaded when certain operations occur. Having a few hundred redundant context menu entries in the registry really slows things down.
    – Polynomial
    Feb 8 '12 at 16:44

No-no, It's bit rot! ;)

Seriously, a windows installation does not degrade much if you don't use it at all. But a computer you're using will much likely have more and more software installed, many of wich automatically set themselves up to start running in the background on startup. In fact all computers, no matter what OS, can be expected to run slower as more and more services is running. Windows is perhaps notorious for allowing programs to install themselves in the "startup folder" or similar.

There allso seems to be an apparent loss of responsiveness with many programs installed, even if they are not running; I'm not sure what causes this, but a random guess would be that there is a bit more data to parse through each time a menu is displayed wich subjectively slows the computer down without really impairing the average processing power...

  • 1
    I can only partially agree. Not using the computer will keep it at equal performance (none). However this issue is not universal, I keep a fairly clean OS. This means installing and uninstalling lots of apps, Windows is the only one with a problem in that respect. Nov 20 '08 at 19:39
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    This is a sort of "tragedy of the commons" problem. Many programs set up a constantly running agent to improve it's own startup time at the expense of the rest of the system. Mar 2 '10 at 23:54
  • “a windows installation does not degrade much if you don't use it at all” — I think this is true of all computers. They work perfectly until people start using them. Then all bets are off. Apr 7 '10 at 11:28

Not sure what you're asking about without any more specifics. Older versions of Windows had some issues, but I've found XP and Vista to be pretty solid, to the point where I can leave them running for a couple weeks without a reboot and don't see any problems. I'm sure that certain software combinations might cause problems, but Windows itself (at least in recent versions) doesn't seem to degrade in performance.

  • 1
    He is talking about the performance of an old windows install versus a fresh install. Not windows being up for a week versus fresh boot. Nov 20 '08 at 17:23
  • What good is windows itself without the soft?
    – Trufa
    Mar 1 '11 at 14:41

On the other hand, even a clean reinstall won't make an old computer feel as fast as it did when it were new; because we expect more and more. Ten years ago you used smaller simpler applications, wich used less CPU and RAM, today maybe even your word processor is using hardware accelerated 3D effects...

This, I beleave, is the number one cause of this (often not measurable) feeling that the computer is getting slower. (Of course on a windows system there may be measureable differences before and after reinstallation. Windows is a complex system doing a lot of things in the background, and some processes may not do a good enough job cleaning up after themselves. Windows have been criticized for many things during the years, and being to effective and not wasting resources is not one of them) ;P

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    This is not the case, if you do a reinstall, it may not feel fast, but you will get a performance increase from before the reinstall. Nov 20 '08 at 16:47
  • Yes, of course! What I tried to say is that there's a psychological explaination too: the fastest computer on the market feels fast, a few years later the same computer feels slower because it's not the fastest computer anymore (regardless of actual performance)... Nov 20 '08 at 16:59

I run Windows XP since 2002, and cannot confirm to the performance degradation claims I ofter hear, except for the boot time.

Every 2-3 years I have reinstalled Windows, for various reasons (repartitioning and not wanting to use a partition manager etc.). After a clean install, Windows boots fast and feels snappy. However, after I install all the programs I need, the boot time is considerably longer, but otherwise there is no change in "snappiness", whether I use the same installation for one day or for one year.

A few years ago I read a test from a German computer magazine, where they compared Windows performance before and after running different registry cleaners, and found practically no differences. I would think the experienced performance degradation comes from installing more programs over time, and especially programs, which run on background. However, I don't believe Windows itself degrades the performance.


When first installed, windows configures disk controllers to use the fastest DMA mode available. If sufficient errors are encountered, the access mode is stepped down. There is no mechanism that tries to use faster modes if things are operating smoothly. Over time, the mode drops further and further, until all disk access is in PIO mode and the computer seems completely broken.

Deleting the controller device forces windows to reconfigure the device using the fastest mode available. A complete re-install causes this to happen.

Pure speculation on my part, but it makes more sense than registry bloat when you consider that people are complaining about bitrot on machines that have gigabytes of excess RAM.

(Certainly additional services and other background processes contribute to slower boot times, but the idea that the performance of the software would degrade without impacting other functions is pretty unlikely)

  • 1
    It sounds like you might have a real hardware problem. I haven't seen such behavior in a while.
    – GregC
    May 21 '09 at 4:57
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    +1 - PIO mode is a sign of hardware problems, but regardless, it does cause an INCREDIBLE slowdown. In addition, those errors can accumulate over a really long period of time, which may not indicate a significant hardware problem but maybe a slight fault, or perhaps you jolted your laptop a few times through its life.
    – Ricket
    Oct 22 '10 at 14:50

I suspect that for many people, it's the accumulation of adware. I haven't done a scientific study, though.

  • 1
    Of course that would be a MASSIVE resource drain, but that can't account for all of it. This very subjective feeling that the computer is slowing down for no reason is very old, long before adware were common. Nov 20 '08 at 16:18
  • Great answer! Every time I get the "my computer is slow, can you fix it" call from family or friends, I've found it infested with adware, desktop widgets, trojans, etc.
    – Sherm Pendley
    Nov 20 '08 at 19:47

It would help to be bit more specific about the situation (how much slower does what get, what are you doing to your machine, etc.)?

I would expect it to get slower as it grows: most data structures work this way.

Make sure your disk is defragmented.

If you install a lot of software, it's common to get a lot of registry entries. Depending on the software, it may not get around to cleaning up its messes when you uninstall it.

Check for adware, viruses, etc.

Like ahockley, I've found that XP and Vista (with recent service packs) are quite stable--at least as stable as Linux PCs that I manage.

  • if you have to reboot your linux PCs for any reason other than kernel updates, you're doing something wrong
    – rmeador
    Nov 20 '08 at 16:17
  • In both cases it's generally "kernel" updates that force reboots. Now that I think about it, Windows has them a bit more often. On linux, sometimes a user will get the machine locked up to the point that ssh fails. For me, it's often just easier to reboot in cases like this.
    – Mr Fooz
    Nov 20 '08 at 16:47

You've asked for concrete evidence that machines running various versions of MS-Windows OS become more sluggish over time. I have also observed this. There are various reasons as to why that may be the case.

  1. registry clutter
  2. more demanding software
  3. more applications loaded into memory and running
  4. malware
  5. hard disk fragmentation

Here is a simple procedure for obtaining the evidence you requested.

  1. Using a stopwatch, time various operations on a specific machine, especially ones that you anecdotally believe have slowed down.
  2. Reformat your hard disk and re-install enough software to complete the following step.
  3. Using the same equipment as before, perform the same timing experiments

This will give you a concrete answer to everything but reason 2 as a lot of software now updates itself with the most recent copy automatically.


Bugs in applications and DLLs (also know as DLL hell). MS tries to fix the bugs but can't because it would break too many apps. So they create a new version of the DLL with a new function -> DLL gets bigger and needs more RAM, takes longer to link dynamically, etc.

If you're really unlucky, the old code demands a copy of the original DLL to be somewhere, so MS even has to give the fixed DLL a new name. This way, more and more bugs clog your memory, PC swaps more -> slow. Other programs have given up on the DLL hell and bring their own versions of the DLLs which they keep in their install directory. Now, you have to keep several copies of the same DLL in RAM.

Then we have a lot of stuff going on in the background. The virus scanners get slower every day because they need to check for more signatures. Junk piles up in the tmp directory, forcing the drive head to travel bigger distances. It takes longer to scan the directory.


There are various patches and updates that Microsoft makes to its software that may play a role here as well as changes in hardware over time.

XP Original requirements for example lists a 128 MB of RAM recommendation that I doubt anyone would try to run XP on that low amount of memory.

My current machines have at least 2 GB of memory which is 16 times that amount and generally I wouldn't run XP on a machine with less than 512 MB of RAM, due to how much memory will get used up as the O/S does all that it does at startup.


The Windows registry, which almost every Windows application uses in one way or another can become very bloated with junk data over time. This is especially true when installing and uninstalling many applications. Often applications don't clean up their registry entries after being uninstalled.

There are applications out there which attempt to clean up the registry and you can do it by hand with regedit but proceed with caution- destroying an application's registry will ofter break the application and potentially the operating system. This is just one area to look for performance gains though, hardware could also easily be the blame.

  • Registry won't affect boot speeds. Startup items and services do.
    – Apache
    Nov 10 '13 at 21:11

My father still uses his IBM all in one XT, running DOS 5.0, WordPerfect 5.1, and Quicken 6.0 to manage his business expenses. It runs the exact same speed today, as it did 6 years ago, when I first set him up on it.

Of course this avoids much of the possible pitfalls described in other answers, No new software installs, no registry, no extra startup applications.

You might almost consider this a control case.

  • 1
    And this is not windows!
    – Ola Eldøy
    Jan 8 '09 at 11:33

Others have given specifics, but I think that fundamentally, this is an example of the second law of thermodynamics.

In a system, a process that occurs will tend to increase the total entropy of the universe.

If you're not doing anything to speed Windows up, it will always get more disordered (and therefore slower) over time.

  • 1
    you can't beat thermodynamics
    – seanb
    Dec 10 '08 at 5:03
  • 1
    This is nonsense.
    – JKAbrams
    Jan 21 '14 at 3:51
  • Only if there's not a link between disorder and performance. I'd say there typically is.
    – amdfan
    May 9 '14 at 3:39

With all the machines I use regularly I've not noticed any slow-down from the day I first used them. Some applications are a little slower, but generally that's because a new version has some out with some new features. Overall there's not much of a difference.

However, the machines which I get complaints about in the office tend to have a huge list of "services" and other applications running in the background. My machine isn't high-spec but runs quick because I make sure that I don't have a huge process-list; on average I've got <50 processes running. The guys in the office who say "my machine's slow" have, despite my requests, installed this or that and soon they've got ~100 processes running (inc. multiple anti-viruses, Yahoo/Google toolbars, etc.). Even when they do uninstall stuff the crapware they install tends to leave services around or small EXEs running.

If you're experiencing a slow-down I'd say it's time to Start>Run>msconfig and cull the rubbish that's booting when you do.


An SSD goes a long way to cure sluggish performance.

I rely on WinDirStat to find large and forgotten files, directories with too many files, and directories with too many directories. That's how I found out about WebsiteCache, by the way.

I use CCleaner to improve registry footprint.

I use ProcessExplorer to find leaky applications.

I use TcpView to keep TCP/IP connections in check.

I use autoruns to keep start-up apps and services in check.

I really hope I someday find a way to clean up WinSxS folder (does it stand for win-success, or is it what I'm thinking).

With these tools, all is well on Windows XP that was initially installed 3 or 4 years ago.


Running software with memory leaks will cause this, as less memory is available for caching. For your average home user, spyware/crapware frequently becomes an issue as well if you're looking at it from this point of view.


Are you sure its not the hardware performance that degrades?

Take some good benchmarks, re-install the system as it was when you first got it, and then measure again. I would be curious to see if the HDD or other components are partly to blame.


Aside from adware, other application developers want to have their application load bootstrappers when windows starts, to reduce the perceived time it takes their application to load, or they want a background service to handle downloading updates etc. Common Examples: Microsoft Office, Google Updater, Adobe Acrobat.

To compare, try opening up msconfig and disabling all startup items and services and then rebooting.

  • Autoruns is good for this.
    – GregC
    May 21 '09 at 4:58

It's not only to do with the registry. When applications are installed, they sometimes install a load of unnecessary junk which even if the programs are unused, then run in the background from start-up. When applications are uninstalled do they always uninstall properly, or do they leave bits of the application and files behind or leave windows still attempting to find, run or use various parts now missing, or have pieces been removed that other programs also depend on? Install and uninstall application programs often enough and eventually Windows itself starts to become unstable and needs a clean install.


It primarily has to do with disk fragmentation and an increasing number of services and background processes as additional software is installed.

Vista solves disk fragmentation issues very cleverly: So cleverly that Vista machines tend to actually increase in speed over time. On the other hand, installing lots of services can drag down Vista just like it can XP.

Windows 7 also has the Vista features that prevent the OS from slowing down over time due to fragmentation.

Note that "fragmentation" in this context refers not only to individual files being fragmented but also to collections of files that are loaded at the same time not being together on the disk.


The problem is that Windows does not have a repository for software, Linux have all its software organized by some dictated install software (apt-get, etc.) while in Windows land each man is for itself, you can install anything, anywhere and who watches everyone is the registry.

The problem is not Windows itself, but rather how the applications use the registry. In Linux each file of a program has a place to be and the dependencies are handled manually or by some master control software. In windows the person who made the application also has to make an uninstallation program. Well, you usually don't want the user to uninstall your software and if the user does that you don't usually care about what happens to the user.


I agree that Windows slowdown is a fact of life for any Windows system (although I haven't used Windows Vista or Windows 7 much, so I can't comment).

Aside from registry fragmentation/corruption and hard drive fragmentation/and corruption (worth running chkdsk with an F parameter from time to time), I think installing applications that add themselves to startup but more often as services is a big contributer to slowdowns. They take time at startup and take resources during general running. One on its own probably won't make a difference, but the build up of them over time does. It's worth taking a look at the list of services running on your machine and changing their startup options if you don't use them. Make sure you investigate exactly what they do first though.

Starting up itself can be quite a resource hogging task also. It's worth defragging the start up from time to time with a free, Microsoft supplied application, called BootVis. This will profile your machine during startup and reorder (defrag) anything that needs to be loaded on start up so that it loads faster, for example, drivers.

Browsers also can get loaded with add-ons and toolbars over time which will also slow down your perception of the system. I think it's worth uninstalling unused add-ins from time to time.

The best result does come from a fresh install, though. It is very interesting to read that other OS's don't suffer this problem.

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