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Why does the /winsxs folder grow so large, and can it be made smaller?

My machine has been running Vista Ultimate 64-Bit for about two years now. ServicePacks SP1 and SP2 are installed, too. The system partition has a size of 55 GB, which should be quite comfortable under normal circumstances, but about 40GB (no typo) are used by the Windows-Folder, especially the subfolder winsxs, which takes about 35 GB. I have already uninstalled as many programs as possible and did run compcln.exe, to reduce it, but this only gained 2-3 GB.

What can I do to clean up without risking system stability? I'm a software developer and this is my daily work environment, which means - I can't risk to get strange side-effects from blindly deleting stuff. - You can maybe deduce some typical usage patterns from this information.

Any suggestions?

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marked as duplicate by random Jul 3 '10 at 2:02

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Are you sure it actually takes up so much space? Many files inside WinSxS are actually hardlinks, not copies, of files elsewhere. Two hardlinks take only so much space as one. However, Windows Explorer still counts both as separate files. – grawity Jun 11 '10 at 18:19
I did not explicitly verify that, but as my harddisk reports only few space remaining and total disk size is correct, so I fear it's real. I got the figures from Windows Explorer and TreeSize Free. – Simon D. Jun 11 '10 at 19:00
Explorer and TreeSize Free aren't hardlink aware. – afrazier Jun 12 '10 at 0:59
I suppose that the partition sizes and total disk-usage (in computer-overview) figures are reported correctly from Windows Explorer, is that correct or can these also be distorted by hardlinks/junctions? That would mean quite a bad bug in Vista, wouldn't it? If these figures are ok, than the size of winsxs will not be too far away from the real, physical size, regardless of potential inaccuracies due to hardlinks. – Simon D. Jun 12 '10 at 8:15
Dupe:… – Hello71 Jun 17 '10 at 1:20

You can't delete this folder. It's the assembly cache.

From TFA:

The Winsxs folder, stores multiple copies of dll's in order to let multiple applications run in Windows without any compatibility problem.

Link is:

EDIT: compcln.exe, part of Vista SP2, allows you to remove RTM and SP1 files from the cache, but it will not allow you to roll back to a previous version if you wanted to. The Service Pack Clean-up tool is a replacement of Vsp1cln.exe from Vista SP1 that did much the same thing. See more here.

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Yes, I can, at least major parts of it. ;) +1 for your link, as this has been exactly the one that led me to the existence of tools like compcln.exe before posting the question. – Simon D. Jun 12 '10 at 8:22
compcln.exe will stop you from rolling back or repairing your computer, so it is ill-advised. – user3463 Jun 15 '10 at 20:11
I'm not interested in rolling back to before any service pack, so it doesn't hurt in my case. – Simon D. Jul 2 '10 at 13:02
As long as you're happy with that decision. I'll update my answer. – user3463 Jul 2 '10 at 19:09

I would suggest you to leave the files there unless you really know what to delete. Winsxs folder is where windows store old version of dll files required by some applications. Your vista won't die if you delete them, but some program will.

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Thanks for this advice, although it does not effectively solve the problem. At least it helps not making it worse :) – Simon D. Jun 11 '10 at 19:01

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