awoolford - The utility 'Eraser' you recommended works well, but 'securing' 'unused disk space' with a US DoD 7 pass overwrite takes about 5 hours on my 120G HD.
I would hate to think how long the Gutmann 35 pass would take, probably 25 hours !
I do wonder having my HD spinning continuously for 5 hours does to the life of it !
Why not just defrag, and fill the 'dead' space up with 'any old data', ie. a few DVD's and then delete that data.
That way at least you know any slack space will be overwritten by harmless files even if soemone does try a recovery of data ?