You say you've got 30% of a 40gb hd remaining... that means you have 28gb of files on this machine? What in the world do you have taking up all that space? Could it be just too much stuff running? Are you running every service in the book? IIS, etc? Do you need to?
Take a look here (use at your own risk) to see if you are running anything unnecessary.
http://www.blackviper.com/WinXP/servicecfg.htm>I've deleted all my history files and done a "disk cleanup", what else should I do?
Wayne Myers, MCSD
Senior Consultant
Forte' Incorporated
"The only things you can take to heaven are those which you give away" Author Unknown