When using the Disk Cleanup, if you never want to "Compress Old Files" (which is often annoying and takes a long time) follow this tip:
Locate and then click the following registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Compress Old Files
On the Edit menu, click Export, in case you change your mind.
On the Edit menu again now click Delete.
Thanks to Microsoft for this tip:
http://support.microsoft.com/default.aspx?scid=kb;en-us;812930
