After installing Windows Vista Service Pack1 you can find that free space of your vista drive reduces significantly. The additional space used and occupied by Vista SP1 is used to store Vista RTM files so that system can be reverted to old RTM version when users decide to uninstall the service pack.

If you have installed SP1 and decided to keep it, Microsoft has packaged SP1 with Vsp1cln.exe File Removal Tool to reclaim disk space.

To run Windows Vista SP1 File Removal Tool, open a command prompt (Cmd) or simply press “Winkey + R” keyboard shortcut. Then enter the following command:

Vsp1cln.exe

Once cleaning process completed, several hundreds megabytes of disk space will be freed, depending on edition of Vista installed