Sorry, I hit send button before I was finished. If you go into Command program (old DOS interface which you access via Start Menu/Command and then at the prompt type Format C: /P:7 /X, it should wipe out your whole disk and remove any traces of what was on there. (I don’t know if you even need the /X).
You will then have to reinstall your operating system and all programs. If you have the original windows CD, you would insert into the CD drive and then follow the instructions to reinstall everything. This can take about 2 hours sometimes. You must have all the original disks, though, as sometimes there is a second Drivers and Utilities disk.
But to physically destroy the machine seems like a waste.