I don't know what's wrong with my PC, but i have P4 S478(whatever), 512MBRAM DDR, NVIDIA N6600 AGP, SOUND BLASTER X-FI PLAT1NUM =] and i still play CS Source on 40 FPS. So i need a new graphic card and new RAM. And i heard of SLI and it is very good so maybe i'm gonna buy it.