Fan Failure

[Pker]

Something is wrong with my computer or video card but I'm clueless about what to do. Whenever I turn on my computer it makes 2 beeping sounds. The first thing that comes up is a black screen saying "Alert! Previous fan failure!". I then have to press F1 for it to turn on all the way. I'm almost sure this error is the reason my performance goes to shit after about 30 minutes of game play. Whenever I restart it, the pattern repeats (30 minutes of good performance). I've dealt with this for a while now, but I found out how well my brother's video card (my old one that I gave to him) is holding up. His fps never goes below 100 however long he plays CS. Mine slowly continues to drop the longer I play. He has an AGP Geforce FX 5500 (about 50$) and mine is an AGP Geforce 7800 GS OC (bought 350$) and we both have the same type of DELL computer. Right now his video card works better than mine...but it doesn't have any errors. If you know anything about video cards or computers please tell me what you think I should do to fix this problem. ...And yes my brother is Calik.