Destroy HDD

what is the best command line operation to render a HDD unreadable from within windows? 
or any other free program maybe?

>>28
oh, well in that case
1)Reverse engineer windows
2)turn it into *nix
3)?????
4)Profit

then again, we could just eliminate steps 1 and 2 with just step 1)reinstall with *nix, but that wouldn't be good enough for you windows fags would it?