Recently, I was trying to free up some disk space on my C:\ drive. Back in the windows XP era, I used to delete the hidden blue folders (compressed folders with funky names like $NtUninstallKB975025$) in c:\windows\ that contained the uninstall information of each and every update. In windows Vista SP2, Microsoft provided a cleanup tool to do so. Simply open a command prompt (start+R, type “cmd” and press enter) and run “Compcln”. If you have UAC enabled you will get a prompt to allow the program to run. Click continue and then answer “Y” in the command window that will pop up. This will delete all the unnecessary files that are required to uninstall the SP2 (what’s the point of doing so since SP2 increased tremendously the OS’s performance?), freeing up a lot of disk space.
PS: For windows vista sp1 you can use the vsp1cln.exe tool.