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Wednesday, February 3, 2010 - 11:52 pm ET

Is Half Your Hard Drive Taken by WINSXS

I came across an issue today with a computer that I hadn’t been familiar with up until this point. I know a common complaint from Microsoft users is that the PC’s hard drive seems to mysteriously fill up with files.


My boss’s computer seems to sucking all of space and time into a folder named "WinSxS". Currently the folder is at 20GB of space I think. That’s almost half the entire size of the hard drive.

After doing a quick search online about what might be causing this WinSxS issue, it seems to be a fairly common problem. The kicker is that there doesn’t seem to be any real solution to the problem. What I’m not sure about is if it really started with Vista or not.

My boss is running Windows Vista Business, the web search results say people are experiencing it with their Windows 7 machines too. I’m running Windows XP Professional still, and my folder is less than 1GB in size.

Do you keep running out of hard drive space? Go take a look at this folder and see what size it’s consuming on your drive. Let me know what you find and what steps you’ve tried to take to resolve the issue if anything.

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  1. By Jake Stichler
    316 days ago

    Thanks for the tip… 12.7GB here. Hadn’t even noticed, with a 500GB drive. The majority of the folders (98% or so) are from when I built my system. Mostly looks like garbage that the disk cleaner ought to take care of… but doesn’t. Stupid DLLs… stupid Windows… No good solution to this one but to move to Linux again.


    • By lets revolt
      35 days ago

      12.7 GB – we need to revolt and break microsoft into smaller pieces and make it illegal to force feed us shiit like their mail system, and any other options which are not really options because they bundle all the shiit together and take up our entire hard drive soon so they force us to buy buy buy. OFF WITH THEIR HEADS

  2. By NikosL
    316 days ago

    I reinstalled Vista two months ago. My current Winsxs folder size is 10 GB and it contains 48.752 files & 12.438 folders.


  3. By Real Time
    316 days ago

    I am so glad Linux doesn’t have these issues. :)


    • By csmyth
      37 days ago

      well if linux did half of what I want I’d switch too . . . it has been a 10 yr wait thus far . . .

  4. By daveb
    316 days ago

    Winsxs consists of mostly hard links so takes up a fraction of the reported space:


  5. By Jonathan Donais
    316 days ago

    Trying to explain the reasons why the WinSxS folder (Windows Side by Side) exists and why it is very large is a very complex subject. WinSxS has a long history of development, the main components in this folder are ‘Side by Side Assemblies’ and ‘Manifests’. It was first used in Windows ME and further developed in XP. It has finally become matured in Vista. This folder has many functions.

    I’ll focus on just a couple of the many functions here.

    1. The WinSxS\Backup folder:

    In previous versions of Windows, such as XP there was a component called ‘Windows File Protection’ which was used to make sure that all of the many system files were protected and backed up. These files were backed up in the %systemroot%\System32\dllcache folder. If you had a problem and lost a system file or one of these files had been corrupted, you could run the ’sfc /scannow’ command and the files would be replaced with the backed up copy in the dllcache folder. The dllcache folder was typically 500MB or larger.

    In Vista, ‘Windows File Protection’ has been replaced with ‘Windows Resource Protection’ which, essentially performs the same function. The ‘dllcache’ folder no longer exists in Vista, it has been replaced with the

    %systemroot%\Winsxs\Backup folder. This folder is NOT ‘a backup of a backup’, it exists only to make sure that files required for Vista to boot and operate are protected.

    2. Manifests and Assemblies:

    Vista comes with a default selection of ‘Shared’ Manifests and Assemblies. This huge selection does not slow the system down or effect performance in any way, since the only time these components are actually loaded is when an installed program calls one of these components to be loaded. Developers may include a manifest in their program that calls one or more of these assemblies or they may install their own, private assembly in the WinSxS folder or in their own applications folders.

    When a program is started, if this program specifies an assembly dependency, side-by-side first searches for the assembly among the shared assemblies in the WinSxS folder. If the required assembly is not found, side-by-side then searches for a private assembly installed in a folder of the application’s directory structure.


    1. Duplicate files. Searching for and deleting duplicate files has always been something that Windows users have performed in an effort to reduce used hard drive space. However, this was done because hard drive space was very expensive and hard drives were very small.

    If this was 8 or10 years ago, this would still be a viable option, but it no longer applies since hard drives have become so large and very inexpensive. When Windows XP was first released, a typical hard drive cost around 2.99 USD per GB. Today, you can find a 500GB SATA 7200RPM hard drive for much less than 100 USD. The typical cost of hard drives is less than .15 Cents per Gigabyte. This means that a WinSxS folder that is 6GB costs around .90 Cents, and uses slightly more than 1 Percent of the drive. That’s about the same cost as a large bag of potato chips.

    2. Deleting components from the WinSxS folder. As I explained, the shared and private assemblies, manifests, backed up system files, etc, are critical to the operation of Vista and all of the installed programs. If any of these shared assemblies are removed and you install a program that requires that assembly, the program will simply refuse to run, period.

    3. Every system is different, when deleting components from the WinSxS folder, what works for one system, will not work for another system. Different systems, even if they have the same version of Vista installed, will typically have many different programs installed. A removed Side by Side component may not effect one system, but will effect another.

    4. Changing permissions on or compressing the WinSxS folder can cause problems when installing an OS hotfix and installation/un-installation of any Win32 assemblies.


    • By Gert
      122 days ago

      It is all fine to say that hard drive cost’s has come down and thus the size does not really matter, but try running a couple of hundred Virtual desktops and see what effect it has.

  6. By pcm
    118 days ago

    `The typical cost of hard drives is less than .15 Cents per Gigabyte’

    I would like to buy a 1TB drive from you. Please send me the drive and I will pay you $1.50 (because 1000 x 0.15 Cents = 150 Cents = $1.50).

    Please learn to use a decimal point correctly.

  7. By Russell Thamm
    316 days ago

    Got any idea what this directory is for?
    No, I thought not.
    In case you are interested – this is the directory where side-by-side assemblies (ie DLLs, dynamic libraries) are stored. It started with DotNet. Before DotNet, DLLs were mostly stored in the system folder. You will notice it more under Vista and Windows 7 because XP itself doesn’t use side-by-side assemblies and so stores all its DLLs in the system directory.
    Side-by-side assemblies can use more disk space because you can have multiple versions of the same library installed and thus you can run programs which require different versions. With the old system, of course, you could have multiple versions of the same library but obviously not all in the system directory.
    I doubt that side-by-side assemblies actually increase disk usage significantly, they just put everything in the one directory. However, this would be a useful exercise – far more useful than merely looking at the size of the WINSXS directory.
    As for the Linux – do a search on your disk for dynamic libraries (*.so). I suggest that you will find that dynamic libraries consume a considerable proportion of your disk space. Its just not so obvious with Linux as these libraries tend to be spread all over the place.
    One last comment, trying to run Vista on 40 GB of disk space is absurd. My XP PC which is almost 10 years old has 80 GB.


  8. By Julian Perry
    316 days ago

    WinSXS LOOKS big, but it isn’t – really.. It contains a whole lot of pointers for files stored both within, and elsewhere, and is vital to the PnP and device management system. Whilst seemingly containing multiple files of different names, most of them point to the same file (or sometimes to an unused stub), thus “inflating” the amount of disk space it actually uses.

    Over time, unneeded entries will be scavenged from the system – but they don’t disappear immediately when associated programs or devices are uninstalled.

    LEAVE IT ALONE – things will break if you go meddling.



  9. By wekebu
    316 days ago

    Dual booting:

    Windows 7 RC 7100: 3.98 GB = 28,476 files, 6,617 folders.
    Vista: 10.4 GB = 46,922 files, 11,930 folders.


  10. By Real Time
    316 days ago

    …just one more thought here. Seems everybody is saying “yeah, I have one” but nobody is saying if it is cool to delete it or not. Come on, somebody delete it and tell us if your system still runs!! :)


  11. By waika
    316 days ago

    Ok! I just dleted mine an it 54$5


  12. By Jim
    315 days ago

    I installed Windows 7 Ultimate (64 bit) earlier this week and mine is already up 5.8GB


  13. By Gerry
    315 days ago

    It is definitely NOT ok to delete this folder. As the author has pointed out there was no safe solution to this outside of reinstalling from scratch and then it will only just come back after a while.

    This same thing happened to me back when I was running vista, but thankfully just like the other guys here I’ve switched over to the beautiful world of Linux (Ubuntu Karmic).


  14. By Jake Stichler
    315 days ago

    Real Time, everywhere I’ve seen says no to deleting it. It’s mostly different versions of DLLs that different programs may be using, and supposedly the only safe way to shrink it is to get rid of applications that you don’t use anymore.


  15. By hidden object pc games
    312 days ago

    Wau..I didn’t even know about this..thanks guys for all the information. =)


  16. By Bebeth
    300 days ago

    I was looking from a long time ago, a way to get rid-off this folder or part of it…

    I think now thats not a good idea…

    But, as someone have tried to delete it and got bad things of that tried (Thanks to you “waika”), for mi part I’ve tried to compress it…

    It’s not a easy-simple job, getting ownership and and be granted full control on it… HARD, LONG, PATIENCE…


    Up to now (after 5 days), the only problem I’ve seen is it take a little bit more time to boot. I’ve activate the verbose mode when booting, and it seem to take more time in the first boot sequence, when the listing of drivers is shown. It take twice the time as it was before…

    But I have not install anything yet, no progs, update, or anything else, nether uninstall something…

    I’ll keep you posted if I see something else…

    Don’t be shy to ask if you have any question…
    Acer laptop Aspire 5100
    Ram: 2G
    Hard drive : 120g Splited in two (60g/60g)
    Vista 32Bit SP2
    Winsxs folder size: 6,86 GB / 4,91GB Compressed / 35,234 Files / 9,169 Folders


  17. By Gert
    122 days ago

    Microsoft spin artist?


  18. By Cody B
    98 days ago

    “By pcm
    20 days ago

    `The typical cost of hard drives is less than .15 Cents per Gigabyte’

    I would like to buy a 1TB drive from you. Please send me the drive and I will pay you $1.50 (because 1000 x 0.15 Cents = 150 Cents = $1.50).

    Please learn to use a decimal point correctly.”

    HAHAHAHA. i love it!. I’ll sell you as many terabyte hard drives you want for $0.15 per gigabyte. should turn a nice profit off ya, especially considering that they can be had for a little as 8 cents per GB lately. In case you haven’t realized it yet, it is actually you who is the one that needs to work on your math skills…


    • By Bruce
      91 days ago

      Actually, if you were to read both the original post and Cody B’s response, it is $0.0015 / GB that was quoted. “0.15 Cents per Gigabyte” is LESS THAN 1 cent and Cody B is correct.

  19. By Bruce
    91 days ago

    Sorry, meant pcm’s response…..

  20. By moxy
    62 days ago

    see answer here –


  21. By Tom
    55 days ago

    I have been running XP for over two years on a machine, installing and uninstalling many programs and Winsxs is about 40MB.


  22. By wouldnt youlike toknow
    30 days ago

    i say it’s full of software which has already taken over your system and is spying on EVERYTHING you do on your computer. explore your system folders and files a little closer and you might be surprised what you find.


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