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What is the Winsxs Folder?

Vista Ultimate:

Just wondering. Something new to Vista. C:\Windows\Winsxs uses more
space than \system32 (which is a lot). What is this folder for?


The Winsxs folder includes all manifests, optional components and 3rd party
Win32 files.

The files in %windir%\system32 are hard links to the winsxs directory.

Have you installed a lot of software?
No. Just office 2007 and 3 or 4 small apps.

I did though, come across a Vista article on TechNet:

"Finally (though this doesn't relate to image size), take note that there is no longer
an I386 directory. Instead, all components, whether installed or not, reside in the Windows
directory (although not in the standard SYSTEM32 directory). When installing a new component,
the necessary files will be pulled from this location."

I am guesing maybe \windows\winsxs is where these files reside? That would explain the size
of the directory.
Interesting - I hadn't noticed that before. I see on my dual boot system
that the Winsxs folder on XP is 20MB and on Vista is3.5GB. After studying
the Vista files a bit, here's how it looks to me. First a little
background -

Sxs stands for side by side versioning. This was an feature first
introduced, oddly enough, in Windows ME and of course improved in XP. It
was Microsoft's solution to the "DLL Hell" issue that plagued Win 9x and
provided a way to support multiple versions of same named DLLs. Windows
would recognize a potential conflict and place an incoming DLL in the Winsxs
tree rather than overwriting it elsewhere, would store applicable registry
data, etc.

In Vista the use of Winsxs seems to have changed and been greatly expanded.
Vista includes the Net Framework as a core technology (i.e. and not as an
add in). Many of the files under Winsxs are related to the use of managed
code -headers, manifests, etc. Also, I concur with your thought that this
replaces the I386 folder. It seems to be a repository for installation
files as well as Dlls etc.
Thanks for the info ! I didn't realize Winsxs was in previous versions of Windows.
I never noticed it... I did check a WinXP Pro PC and the Windows\Winsxs folder was only about 30MB.
(Maybe that's why I never noticed it.)
Re: What is the Winsxs Folder? DANGEROUS!

This looks extremely dangerous and I recommend not to try it. The program
is a batch file that could trash the system if interrupted. It doesn't
include an instruction file (as claimed on the linked page) and it's logic
is highly questionable.