Recently Microsoft announced Windows Vista SP2. Vista SP2 offers more compatibility, reliability, and performance, as compared with SP1.

Vista SP2 has changed the Vsp1cln.exe tool to Compcln.exe, which was integrated into SP1, but it is no longer a part of the SP2.  However, the basic functionality has been successfully preserved.
SP2 also includes a Service Pack Clean-up tool (Compcln.exe), which helps restore the hard disk space by permanently deleting the previous versions of the files (RTM and SP1) that are being serviced by SP2.
How To:
1. Open Command Prompt as Administrator (when UAC is enabled) and click on Continue to jump ahead.
2. Execute the command Compcln.exe
3. It prompts to make SP2 permanent on your computer. Press “Y” to confirm!