Cyberscrub is probably the best scrub software you'll find. It has a nifty feature where it will take files from the recycle bin and scrub them off the HD, so you don't have to go through full-disk scrubs as often. Will also find all the various places that Windows stores data about web sites you visit (in the registry?! Go figure...), and scrub that too. Very customizeable, all sorts of useful features, and not particularly expensive.

I don't know anyone that's done a forensic analysis of a Cyber-scrubbed drive to see if it misses anything, but I might take that on as a project one day soon..