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I installed windows 7 many months ago on my laptop, and I don't exactly remember, which method I followed for installation : whether clean Install or startup repair. I find memory shortage and when I searched for items to delete, I found a folder named "windows.old", which is 44 GB fat. Can I delete this folder, if it is of no use for current windows ?

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marked as duplicate by techie007, Tog, Carl B, Mokubai, mpy Aug 19 '13 at 13:34

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If you don't need anything from your previous Windows installation, just select the windows.old folder and hit Shift-Delete > Yes. You don't need to go through the Disk Cleanup route for this. If you have documents, photos and other stuff you need to recover from your previous installation, rummage through the 44GB of data first. Once you found and moved everything you need to a safe location, then do what I told you. –  ADTC Aug 1 '13 at 7:57
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3 Answers

You absolutely can delete it, take a look at the Microsoft Suggested Way to remove the Windows.old folder:

How do I remove the Windows.old folder?
If you install Windows 7 by performing a custom installation and don't format the partition during the installation process, files that were used in your previous version of Windows are stored in the Windows.old folder. The type of files in this folder depends on your computer. After you’ve used Windows 7 for a while—for example, one or two weeks—and you’re confident that your files and settings are back to where you want them to be, you can safely reclaim disk space by using Disk Cleanup to delete the Windows.old folder.

  1. Open Disk Cleanup by clicking the Start button. In the search box, type Disk Cleanup, and then, in the list of results, click Disk Cleanup.
  2. If you're prompted to choose a drive, click the drive you just installed Windows on, and then click OK.

  3. In the Disk Cleanup dialog box, on the Disk Cleanup tab, click Clean up system files.

  4. If you're again prompted to choose a drive, click the drive you just installed Windows on, and then click OK.

  5. Select the Previous Windows installation(s) check box, and any other check boxes for the files you want to delete, and then click OK.

  6. In the message that appears, click Delete Files.

In my opinion, that method is excessive (but I always clean install anyway). Just verify that you don't need anything in there and delete it however is most comfortable, their method may be more clean.

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The disk cleanup is also showing "service pack backup files" and "system memory error dump files". I've no idea of what these files are. Please suggest me, whether I should delete these files too or not ? Are they of any use or not ? –  Rubbal Bhusri Jul 31 '13 at 21:15
    
Sounds like junk to me, but you may want to keep the newest version of the files. One thing that takes up tons of space is Windows Restore Points, if you right click on "My Computer" and select properties, then Advanced on the left, you can limit the system restore disk space (or remove it all together, which is what I do). –  nerdwaller Jul 31 '13 at 21:28
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Go to start, type in "Disk Cleanup" and wait for it to finish scanning. Next, select "Cleanup System Files" and wait for that one. One of the boxes will be Old Windows Installations, and you can select it and have windows safely clean it out.

You can't do it yourself because some of the items have restricted permissions, are read-only, or are recognized as system files.

This is the safest way to do it.

Go through it first (your user's documents and pictures) to make sure you have everything out of it before you erase it.

The erasure may take some time.

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The disk cleanup is also showing "service pack backup files" and "system memory error dump files". I've no idea of what these files are. Please suggest me, whether I should delete these files too or not ? Are they of any use or not ? –  Rubbal Bhusri Jul 31 '13 at 21:15
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It depends on you, your usage of your system, and how OC(D) you are.

You used the clean install method to re-install; the Windows.old folder is a copy of your previous Windows installation.

As such, it will contain the drivers, registry hives, system settings, Windows Updates, and everything else that goes in the Windows folder from your previous installation.

Much of that is disposable because they can be gotten again with the new installation (e.g., Windows Updates, .NET Frameworks, drivers, etc.) However, you may want to consider a few thing before deleting it since there may be some things you might want to keep.

  • Have you already re-installed all of your drivers? If you have some exotic hardware which you no longer have the drivers for and cannot find a copy, then you will want to copy them from the old installation.

  • Had you installed some software in the previous installation and don’t want to waste bandwidth to download the installers again? You may (depending on what it was) be able to find the installers in the old folder (e.g., Windows.old\Installer, Windows.old\…\Installation Cache, etc.)

  • Have you made changes to settings for Windows or your programs? The registry hives contain a lot of that information. You can mount the old hives and export the settings, then import them to the new system so that you don’t have to reconfigure everything manually. (This is usually an annoying, manual process.)

  • There could be other stuff in the registry (or files) that you want to keep, but again, that depends on your usage and how important it is to you.

One thing to definitely check before deleting it is to look through the user folders Users\* to scan for anything you want to keep like files you’ve created/saved, settings for programs, and so on. (You can also look through Program Files*, but there will rarely be anything you need to copy.)

Also of note is that the actual Windows folder is not actually 44GB (or at least, it shouldn’t be). Windows uses hardlinks to make file entries that are really just pointers/shortcuts, and thus share space on the disk. You can find the actual disk space being used by looking at the Size on disk field in the folder’s Properties dialog:

Screenshot of Properties dialog with Size on disk highlighted

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I didn't get the hard link thing. Does it mean, the repeated use of pointers/shortcuts make heavy ? What space it shares, which make it so fat ? –  Rubbal Bhusri Jul 31 '13 at 21:01
    
The disk cleanup is also showing "service pack backup files" and "system memory error dump files". I've no idea of what these files are. Please suggest me, whether I should delete these files too or not ? Are they of any use or not ? –  Rubbal Bhusri Jul 31 '13 at 21:16
    
@RubbalBhusri, Without hardlinks, if you make two copies of a file, they take up 2x the size of the file. With hardlinks, only one copy of the file is put on the disk and two pointers are made that point to it. The Windows folder is notorious for being “huge” without actually being that big. Specifically, the folder Windows\WinSxS looks like it takes up a lot of space, but those are hardlinks, so it actually doesn’t take up much space at all. Therefore, if you delete WinSxS, the free space doesn’t actually go down. –  Synetech Jul 31 '13 at 21:16
    
The disk cleanup is also showing "service pack backup files" This is because either you had originally installed Windows 7 “gold”, and then installed SP1 on top, or it just contains old files that were changed with Windows Updates. If your system is working correctly after the updates, then they should be safe to delete. and "system memory error dump files". When your system crashes, Windows makes a copy of the system memory to a file so that you can diagnose the reason for the crash. These are usually safe to delete since you probably won’t be using them. –  Synetech Jul 31 '13 at 21:18
    
So-u mean to say that even if I perform disk-cleanup on window.old which seems to be 44 GB fat(but not in actual due to hard liks thing), I won't gain much space. Well Disk-Cleanup dialog box is showing that it's gonna free 28 GB of space. Is that figure a fake one ? –  Rubbal Bhusri Jul 31 '13 at 21:42
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