Help asap! My laptop has numerous viruses and i need to know how to wipe it!

Aparently after much scanning with avast,norton antivirus and adaware, my lap top is infected with:
Trojans
Vundo virus
and adware

I get pop ups, insanely long loading times, and my task bar always shakes.

I tried all virus sweeping/removal things i could and the viruses keep restoring themselves. I want to wipe my whole computer and start new but when i put in my windows xp disc and try to re install it freshly new some messages show up saying that i cant because the computer has viruses. what do i do?