Help, I dropped my desktop!

During a move my desktop was dropped about 4 feet. Since then, the fans come on and it freezes after doing the smallest amount of thinking. It’s only good for email (without video) and itunes. I’m assuming it’s overheating. That, or the heat sensor was damaged??? It’s an hp m.c. w/athelon duel64 and 1G ram. Had it for 12 months. Any help would be appreciated.