the trouble with using the microsoft cleanup tools is they don't get rid of everything (hardly anything actually - more conservative that margaret thatcher with a public utility
if you look in
C:\Documents and Settings\<yourname>\Local Settings\Temp after running ms cleanup you'll see....
it won't reliably delete anything but .tmp files
(and will also leave the sub folders and contents) -
often it will leave more than it cleans nor will it delete the update files
or logs - could leave the best part of 1Gb and 1000s of files
(that's why I use ccleaner -
http://www.filehippo.com/download_ccleaner/)
don't let it install yahoo toolbar -
do use the default settings
if you bank - clear the delete cookies option
I rarely trust free utilities - this is one of the few exceptions
the worst damage it's ever done is clearing my banking password
do all that first - then check the disk for errors
finally defrag
repeat every couple of months