Remove Service Pack Files

To make a service pack permanent, and remove the service pack uninstall files, run the following commands:

Vista SP1 – vsp1cln.exe
Vista SP2 or Server 2008 SP2 - compcln.exe
Windows 7 SP1  - DISM /online /cleanup-image /spsuperseded

reference: http://support.microsoft.com/kb/2795190