Hi my pc had a virus that shut the whole pc down and i didn't have the windows disc to get it back up and running.

So we got someone in that got it running again but there is loads of programs with missing files ect. i've just got hold of a brand new windows xp pro and want to wipe the whole harddrive then install the new windows xp.
There is nothing on the harddrive that we can't reinstall, so can someone please tell me how to wipe the drive clean?
Cheers