id guess he has a pile of worm,trojans ,backdoors ,ect and exspecially spyware (kazaa is full of that junk )
the fastest way to solve the problem is to do a reformat .
the otherway is to identify each and every bug , clean out all your temp files,temp downloads, any .exes,files that you got from kazaa,ect . and do the regedit to it . if its a worm thats attached to all your .exe's then you would have to edit in safe mode, and address each one of those also .
if your not familier with the registry (regedit) in windows then your just better off to reformat.