Lock ups on everthing

My GF has a dell XPS 210 had it for about a year adn half.  3 days ago it started to lock up... open the net its locks up open my computer its locks up..... try to copy stuff to scan from thumb drive ..system locks up. I mean even screen saver locks it up. Now its a lock up that u can still scroll around with the mouse but u cant click on anything nor can u ctrl atl delete the only thing u can do is hit the power button.    Heres teh funny thing she plays WOW and for what ever resaon she can jump on there and play and naver lock up .... Anyone have any ideas i can do  to find out whats going on and fix it.