Sounds like a driver problem, rather than virus, have done a search for you heres one solution
http://www.techspot.com/vb/all/windows/t-15393-Infinite-Loop-Fix.html
My laptop as ati card in it, when i first got it i had problems with freezes and things, used a program called driver cleaner 3 then reinstalled the card drivers, solved the problem, though be very carefull if you go down this route, make sure you have the right drivers before reinstall, hopefully the above link my help before looking at this route.
A WISE MAN ONCE SAID