I can run most of Valve's games on my Dell that's over 7 years old now. It's got a P4 3.0Ghz processor, 2GB of ram (upgraded from 1GB that it came with), and an ATI Radeon X1650 Pro 512MB AGP card (originally it came with a Radeon 9800 Pro 128MB card, which blew after 3 years), and it runs games like Portal, HL2 + EP1 and 2, Team Fortress 2, and Left 4 Dead 1 and 2, The only Valve game that it doesn't meet the minimum requirements is Portal 2, as they recommend having at least a 2.0Ghz dual core processor, though I never really tried running it on my system.
Since you have a PCI-E slot, you have alot of options... personally I'd recommend something in the Radeon HD 5000 or 6000 series with at least 512 MB of onboard ram. You can find most cards in the low end of each series like the 5450 or 6450 pretty modestly priced online these days, for instance a 6450 goes for as little as $50 on Amazon, and it's all you'll need to run most of Valves games and pretty much any game that doesn't require at least a dual core CPU to run.
On 2/24/13, MB1025 said:
You know I was always wondering why no one ever used the dollar sign for $ony, but then I realized they have no money so it would be pointless.
