ghey screen of death. Can find a good friend with a different video card (nvidia) and borrow it? Then install nvidia drivers and play all your fav games? If it fixes the problem, you have a solution, if it doesn't, then your HD4850 card is probably a-okay and you might need to reinstall the OS or run a registry clean/defrag program or something. Just be careful that you don't use a graphics card that will brown out your 500w PSU.