I have got Norton Systemworks which (within 'utilities') has got a US Government wipe facility for free disk space. After I have periodically cleaned out internet history, cookies etc and defragmented, I do a government wipe (overnight! got caught out the first time it took hours!) so I guess that may be something you could consider. I think this is good practice regardless of your reasons to ensure files and fragments are deleted :-) as it keeps RAM and your machine in general uncluttered.