After installing a service pack for Windows, some files are left behind so that you can uninstall the service pack. If you are sure you want to keep the service pack (most people are) you can save 2-3GB of space by removing these backup files.

In an elevated command prompt, run the following command:

DISM /online /cleanup-Image /spsuperseded

In order to get a command prompt with admin rights in Windows 7 or Vista,

1. Click Start Menu
2. Type “cmd”
3. Press Alt+Enter

or

1. Click Start Menu
2. Type “cmd”
3. Right click “cmd.exe”
4. Click “Run As Administrator”