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I recently formatted and reinstalled Windows on my laptop. It now runs much faster. I have been doing this about once a year for the past decade. Why is this needed?

I always figured this had to do with installing and removing programs, which over time fill up the registry with junk. Is this true? Are there any programs that can tweak the system without reformatting?

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I haven't booted into Windows in months for this very reason. –  Gaz Davidson Nov 19 '10 at 13:52
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XP w/SP1 and no AV software, smokin' fast....its all about what is added after the clean install that slows a system down. –  Moab Nov 19 '10 at 14:20
    
@Gaz: What in the world? You are missing out. –  Flotsam N. Jetsam Nov 19 '10 at 16:19
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I have a corporate managed desktop running WinXP and McAfee. It is perfectly "clean" with only MS Office and Firefox installed. Those are run about once a month. Prior to corporate management and McAfee updates it was smoking fast to start-up and run apps. After a year, with no additional software installed, and practically no browsing... certainly no viruses. It takes minutes to fully startup and Office and even Firefox apps are so slow they are barely usable. I've experienced this degradation over time "phenomenon" with Windows systems for the last decade regardless of usage patterns. –  Michael Prescott Nov 19 '10 at 17:10
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@Flotsam, not really. If it wasn't for the need to connect to customer VPNs using softkeys, I would have deleted my Windows partition years ago when I transitioned from being a Windows power user to a free software hacker. –  Gaz Davidson Nov 20 '10 at 16:44

8 Answers 8

up vote 37 down vote accepted

The registry is a bit of a misconception, The way it works, it could be filled with junk but it shouldn't slow down your machine - imagine, all roads are linked, but just because there is a traffic jam somewhere doesn't always mean it will affect you somewhere completely different!

It is pretty much just software that starts with your computer, updaters and bad drivers.

You can greatly speed up your computer using Microsoft / Sysinternals AutoRuns and delete/disable enries you do not want to start up with your machine.

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"The registry is a bit of a misconception" <-- That's very interesting to know. Do you have any reference for that? –  Hippo Nov 19 '10 at 12:30
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@Hippo - It is from experience, I am currently trying to write a blog post about this, it will probably finished early next week. –  William Hilsum Nov 19 '10 at 13:00
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@Will - will you actually do some tests, for example look at the number of lookups/sec, time to execute, disk queue lengths and so on, or just write about how you feel? –  Gaz Davidson Nov 19 '10 at 13:49
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@Gaz Davidson - Fully scientific! Not sure about disk queue etc, but will be a lot of benchmarks. –  William Hilsum Nov 19 '10 at 13:57
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@harrymc: Saying that "the registry is a simple-minded database" actually means that you don't know how the registry is exactly implemented. You can't talk about the efficiency of the registry without knowing its implementations or doing proper measurements. Your B-trees analogy is really far-fetched, the registry is definitely not a B-tree... –  Tom Wijsman Mar 20 '12 at 13:16
  • You try out lots of applications
    • Due to you computer's configuration, Windows loads in more junk than on a clean install.
    • Software developers believe their apps are so vital that
      • part of them must be loaded at boot time and have icons in the system notification area.
      • they need a special driver (but no one tries to write small drivers any more)
      • they should check something every 5s even if it only changes every 3 weeks
        • availability of updates Wil
        • screen orientation
        • attachment of a phone etc
        • new files appearing that need indexing, adding to albums ...
    • Software developers tend to have the latest Mega-PC, and believe you should too.
      • So people with "slow" PCs should fix any problems by buying a new PC for the app.
  • viruses, trojans, etc
  • anti-viruses, anti-trojans, etc

P.S. I'm a software developer.

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Now, now, we don't all believe everyone has the latest Mega-PC... We just believe everyone SHOULD have the latest Mega-PC!! :) (I also am a developer) –  BBlake Nov 19 '10 at 14:39
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@BBlake - quite right, answer corrected :-) –  RedGrittyBrick Nov 19 '10 at 14:49
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Everyone SHOULD have the latest Mega-PC (I am a software developer.) –  Blankasaurus Nov 19 '10 at 15:13
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Every developer SHOULD NOT have Mega-PC. (I'm a developer.) –  Vasiliy Borovyak Nov 24 '10 at 6:09
    
A Mega-PC isn't always necessarily to develop, unless you work with high end stuff. (I'm also a developer). –  Karolinger Nov 26 '12 at 2:12

The biggest slow downs are:

  1. The crap-ware you keep installing. If you don't use it, un-install it. Before installing anything ever again, do a little research into what the best apps are to do what your trying to do without a lot of overhead (post such a question on SuperUser--you'll get rep points!)

  2. The next biggest thing is your anti-virus and other "security" type software. Throw that all away and learn how to surf safely. If you must download something from an unknown source, run it through virustotal.com before executing. I don't care what they say you can survive just fine without anti-virus software running on your machine. I'm not saying you should shut off windows firewall, just don't add an anti-virus or internet security suites.

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+1 for "throw away your anti-virus". –  Hippo Nov 20 '10 at 12:25
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@JFW: I'm sorry, but you ain't much of a superuser if you're using that garbage. Sounds like you've been brainwashed by those security suite racketeers. –  Flotsam N. Jetsam Nov 22 '10 at 13:37
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@Sirex: Say what you will. I've had to remove too many viruses from folk's pc's that had AV installed & running to fall for that trash. –  Flotsam N. Jetsam Dec 16 '10 at 13:32
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You don't have to throw out your antivirus, but real-time protection is overkill if you are surfing safely. I have MBAM installed and run it periodically whenever I know I'm not using the machine for crtical tasks. Real-time protection is for kids and Aunt Ethel types. –  ultrasawblade Dec 27 '10 at 18:32
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No such thing as surfing safely. I've had downloader attempts off of mainline websites that formerly were trusted websites. Safe surfing now means you don't view blogs, don't use your computer for entertainment, only go to commercial sites that have a vested interest in keeping their security top-line, don't run Flash, Java, Quicktime, etc. This includes Linux systems, Adobe and Oracle spread the vulnerability love everywhere. –  Fiasco Labs May 27 '12 at 16:12

No, even if the registry was massively bloated there would be little impact on the performance of anything other than exhaustive searches (ed. of the registry itself).

is a quote (in the comments) by Mark Russinovich, who is a widely recognized expert in Windows operating system internals as well as operating system architecture and design.

Up to this point nobody has proven him wrong with extensive unbiased tests, that involve multiple reboots, multiple computers, different sets of software and can easily be reproduced. It's one of those myths that get debunked amongst many other so-called performance improvement tips, simple because nobody has even reproducible claimed that the cleaning on its own improves performance. Because really, removing entries that aren't even touched while your PC boots is not going to have much effect.

What mainly slows down your PC are AREs (automatically running entries) which you can clean with AutoRuns, this tool list the following: Logon Applications, (Internet) Exprorer extensions, Scheduled Tasks, Services, Drivers, Codecs, Boot Execution Code, Image Hijacks, AppInit and KnownDLLs, WinLogon, Winsock Providers, Print Monitors, LSA Providers, Network Providers and Sidebar Gadgets.

Over time, these applications themselves load more information which is what makes software like Disk Cleanup come to existence. CCleaner these days does quite well on enumerating most of the files of most of the software you have, however you will want to stay away from its registry cleaning capabilites with have a higher chance of breaking something than giving you any performance benefits.

The most well known locations where this happens are the Temporary folders of Windows as well as caches and history files and folders of your browser, these are files and folders that are actively used and thus play a big role in your performance. Other files may include those referenced to by the registry or by configuration files on your computer. Keeping the amount of software and files / folders on your system to those that you actually might help as well.

So, to summarize:

  • Cleaning the registry does not make the registry smaller, but leaves blank space behind.

  • Compacting the registry to remove blank spaces can be done with NTREGOPT as administrator.

  • The registry itself does not become slower as its size grows.

  • Entries in the registry can affect the performance of your installation, mostly the AREs entries.

  • Files on your system that are referenced by the registry or configuration also play a big role.

  • Make sure you regularly get rid of viruses, software you don't need and cleaning out old files.

Here's what Chris Pirillo from Lockergnome (famous for his TECH on CNN) has to say:

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I tune up customer PCs regularly. While each PC is different, the changes that have the most impact generally are:

  1. Defragment the hard disk and ensure there is at least a few gig free for work space. Move the pagefile to a separate hard drive from the OS, if they have a 2nd physical hard drive.
  2. Remove all those extra processes in memory (use process explorer to see them, use ccleaner to disable). Reducing processes running in memory from 70-90 to about 50 can make a huge difference in speed and responsiveness (this is typical what I see for XP PCs).
  3. Uninstall unneeded programs. This gives back disk space and often removes processes out of memory and out of the startup.
  4. Update OS/applications/firmware - so they are all current. This helps stability and security more often than speed.

I've tried a variety of register cleaners/compactors/etc. over the years, and they've never made a difference I could detect.

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Please note I have changed your username. Since your post is legitimate I am assuming your not a spammer, however please note that having links in your profile is fine, advertising a site, even your own, within posts and as your name is frowned upon. –  Diago Nov 23 '10 at 16:30

The first data written on a hard disk can be retrieved faster:

For a clean install you will probably use only the fastest part of the hard-disk. With an old computer your harddisk is probably full and/or system files (updates, etc) are written to the slower part of the hard disk.

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Since Windows 2000 realized I was trying to understand when and why Windows OSes start to work slowly. And I found the reason and the cure.

The reason is audio/video codecs. Do not install any audio/video codec! Even DivX is not necessary. Codec packs are evil. :) In Windows any installed codec is a windows driver. Any driver slows the boot time and the general performance.

The cure is VLC player. This one don't require any codecs, they are embedded.

Since then all my systems (Windows OSes) almost don't lag, boot fast, and never hangs.

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I'm sorry but "Any codec is windows driver" is a misconception. VLC player is good piece of software, though. –  tomp Nov 21 '10 at 10:29
    
You are correct. Changed to "In Windows any installed codec is a windows driver." –  Vasiliy Borovyak Nov 24 '10 at 6:07
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It's not. It's a direct show filter, which is not a driver. –  sinni800 Nov 10 '11 at 12:27

One case of real-life measurements about how registry cleaning can improve performance is found in the article : Putting Registry-/system-cleanup apps to the test. Please note that to arrive at a situation where registry slow-down occurred, the tester installed CNET’s list of the 20 most popular Windows downloads. This is his summary of the measurements of boot and shut-down :

enter image description here

Here is the explanation of why does this arrive.

The registry is a simple-minded database, and has the distinction of being one of the slowest database systems in the world. In an attempt to somewhat protect it, Microsoft has partitioned it into 5 separate hives.

Over time the registry becomes larger and larger as new programs are installed, used and removed. Even though data is deleted from it when applications are uninstalled, the size of the Registry will not decrease. This is because the data will be marked as blank but remains in place and also because of "left overs" - data that the uninstaller forgot to remove. In this way the registry becomes slower over time, taking longer to access.

There are many products to clean up the registry, but that doesn't help much if one doesn't then also re-compact it, in this way erasing the blank spots occupied by deleted data. As the vast majority of registry-cleaners do not do compaction, they are in effect useless.

A computer whose owner likes to try out software products, installing and uninstalling, may benefit from registry cleaning and compaction, but only after quite many such operations. Please note that any improvement will only show up for registry access, which is normally only a small part of what any normal program does. Some products for whom registry access is a major activity are for example the Windows boot and Installer.

Computers whose setup is relatively static, have nothing to worry about, so have no need for registry cleaners.

Cleaning and compacting the registry is not a 100% process. So once a slow-down is experienced, registry tools may improve the situation, but can never compare for speed with a clean installation of Windows.

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Registry housekeeping for speed is a racket. Wil's comments about the registry are right on. I've had a bloated 5 year old registry that didn't slow me down because I had control over the things I mentioned in my answer. –  Flotsam N. Jetsam Nov 19 '10 at 15:43
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Downvote for the Registry cleaner and defragger links. I'm sorry but those things are just snake oil... –  RobM Nov 19 '10 at 15:58
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@Robert Moir et co. : They are not snake oil for a computer that has seen much install/uninstall of products, but it even so it takes a year or two before they become useful. This I know from personal experience (being a bit of software-maniac), so nothing you can say will change what I said. They are truly useless for a computer seeing only normal usage. However, in all cases, these products cannot totally undo the degradation and so cannot totally restore performance as does a clean install. –  harrymc Nov 19 '10 at 16:19
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And nothing you can say will change what I said. There's plenty of evidence out there that supports my point of view more than an anecdote from someone's personal experience. –  RobM Nov 19 '10 at 16:22

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