XP will not load, neither will anything else!!

I posted earlier today and a very helpful person from
Australia helped.
My son downloaded a virus and destoyed the system.
Briefly, I have now acquired a Kill Disk CD and run it,
thereby cleaning the whole HD.
Guess what?
I ran XP pro set up and it STILL stops at the point where it
should load up windows?
Why is it doing this. The HD is now completely clean!
I have been at it since last night and I have run out of
ideas, so please help guys.

Regards

Chris