<< Stick it in a microwave for a few seconds. >>
Hehe, this is a good suggestion, i really liked it... ;-)
All of your suggestions would ruin ALL of the data on the Harddrive, and if you are going to do that, then use a sure tool, low level format it, fdisk it, high level format it and then reinstall.
If you do not wish to go the long way, just remove the files and fill the HDD with junk files, that will do the job.
Patrick Palm
Am speaking for PC Resources