Soap--> start menu -->settings-->control panel-->system-->advanced--> environment variables. at least in win2k most all windows should be real similar in this respect.
I use to use Bcwipe to wipe my hard drive and temp files blah blah. I dunno if it was good or bad it was free so I didnt complain. It says DoD 7 pass wipe but if it truly is or not I dunno.