All I ever play is Counterstrike:Source - and my PC does fine for me on this. One thing I have noticed is that my FPS stays the same no matter what I've got running in the background (within reason). I used to religiously close everything before loading a game but now I leave it all open - Word, Acrobat, Firefox etc. Even photoshop sometimes. And it makes no discernable difference. I conclude that my system isn't limited by RAM (1024 in my case) or CPU (3200+ Athlon 64). You're in the same sort of situation I'm in (very similar spec). My computer has an AGP graphics slot which is a bit rubbish since you can't get many modern AGP cards. Similarly my motherboard's CPU slot is socket-764 not 939 which means that I can only upgrade the CPU as far as a 3600+ I think, and I don't know if they make them. I'm almost certain your board will be 939 which means you're limited to 4200+. Best bet is to buy a graphics card. You can still get something like an AGP x1950 for £100 ish. Unless you have a PCI-E slot in which case you're laughing and you can choose anything. Like Poopipe says - you need to find out what motherboard you have. Or sack it all off and buy a new PC...