Vista SP1 = C:\Windows\System32\vsp1cln.exe
Vista SP2 = C:\Windows\System32\compcln.exe
Win7 SP1 = dism /online /cleanup-image /spsuperseded

Component Clean (compcln with Vista SP2 or vsp1cln with Vista SP1) cleans up most unused components leaving only the active versions. A very useful tool I routinely use at the computer shop I work at. 

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http://www.iishacks.com/2011/06/23/reduce-windows-7-winsxs-folder-size/

With Windows Vista, the WinSxS folder was able to be cleaned up via a third party tool (WinSxS Lite here – Vista only!). With the initial release of Windows 7, we lost that capability – but it has since returned with Service Pack 1.

The WinSxS folder is used to store install and uninstall files, windows packages (current and previous versions of a component) and out-of-band releases. You should not completely delete this folder. Post Windows 7 SP1, there is now a way to remove the unnecessary files from this folder using the command line (elevated/admin mode -> Click Start -> Type “cmd” in Search. Right click on “cmd” and choose “Run as Administrator”). This is great for reducing the Windows folder size for SSDs and netbooks. In my case it saved 3.5GB of space.

 
dism /online /cleanup-image /spsuperseded


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http://www.iishacks.com/2011/06/23/reduce-windows-7-winsxs-folder-size/


Have you recently installed Service Pack 1?

If so, there is a tool included in the Service Pack 1 installation that will immediately clean up all of the components that it replaced in the WinSxS folder. This tool has been documented to remove up to 3GB from the WinSxS folder. YMMV.

Here is how to use this tool.

***NOTE: After you use this cleanup tool, you will no longer be able to remove Service Pack 1, should any problems occur. Make sure that the system is stable before using.

***NOTE 2: This tool is a one-time use tool. Once it's used it will no longer work on the same installation.

Open Windows Explorer and navigate to C:\Windows\System32. Look for the file "vsp1cln.exe."

Right click this file and select the 'Run As Administrator' option.

The Vista Service Pack 1 Cleanup Tool will remove all of the redundant files that it has replaced.

The amount of disk space you gain will depend on the system, what files are installed, etc.