If you are using a 64-bit (x64) version of Windows Vista, then this is something you should know. By default, the shortcut in the Start menu points to the 32-bit (x86) executable for Disk Cleanup. While Disk Cleanup will work fine from this shortcut for most things, there is one function that does not work correctly – the cleaning of System Restore points and Shadow Copies / Previous Versions.

Note that if you launch Disk Cleanup from another location in Windows, for instance by clicking the “Disk Cleanup” button on a drives properties window, it will launch the correct executable for Disk Cleanup.

If you want to correct the Disk Cleanup shortcut in the Start menu, follow these steps:

1. Click on Start, All Programs, Accessories, and then click on System Tools.
2. Right click on “Disk Cleanup” and from the context menu that appears click on “Properties”.
3. Change the “Target” from “%SystemRoot%\SysWOW64\cleanmgr.exe” to “%SystemRoot%\system32\cleanmgr.exe”.
4. Click on OK. If User Account Control prompts you for consent, click on Continue or provide the appropriate credentials.

Source: Canucky.net