So I have a PS3, but no 360. I've been wanting to play games like Mass Effect, the Orange Box, Gears of War, L4D etc for ages, but could never justify the price of the 360 plus Xbox Live fees. Recently I upgraded my old ass circa 2003 Vaio so that I now have an acceptable hard drive and 2gb of RAM. It's got XP Home with a Pentium 4 2.4GHz processor. I looked up the specs and it's got an open AGP slot (I just figured out what that actually is) so it got me thinking. Can I throw in a video card for around $100 and have a somewhat legitimate gaming rig? 

There's so many cards out there with so many specs I have no idea what I should be looking for. Can I throw in any AGP video card? Is there any other spec I should be aware of that will affect whether or not the card will work in my PC? Finally, anyone have a recommendation for a card?

Well, I can say the AGP is a pretty old format and I wouldnt no it can cut it for the newer games you've just listed.

You can give the Radeon HD 3850 a try: http://www.newegg.com/Product/Product.aspx?Item=N82E16814102730

This is probably the best AGP card available for $100 but It doesnt have a good chance in playing the latest pc games, pci express x16 is the way to go. I would consider that getting a legitamate upgrade wont do the trick. My best advice is the card can probably play those games on the lowest settings possible.

Let me say one thing: AGP is the Wii of PC hardware, but unfortunately without the motion controls.

Even with the best AGP graphics card out there. In combination with your CPU Mass Effect and Gears of War won't run properly.

And this comes from a dude who had a XP3200+ and a 7800GS (2nd best AGP card at that time).

Orange Box and Left 4 Dead should run though. (Medium settings for Episode 2 & Left 4 Dead)

You'll be able to play orange box and l4d with an upgraded video card, but your processor isn't up to snuff for modern games. The system requirements for Gears does say Intel 2.4ghz minimum, but that would be on the lowest settings and presumably look like crap compared to the x360 version.

If I were you, save the $100 or so you'd spend on an agp card and get together $300-$450 for a proper upgrade (mobo,cpu,ram,ps,gpu), assuming you want to reuse your existing case.

I think I'm okay with the games looking like crap as long as they run smoothly. Is that even possible?

For $300+, I'd rather just buy a 360....

Valve games would give you the best chance to run.

Our old Dell computer with a 2.4ghz P4, 1gig of ram and 6800gt could run Half-Life 2 well and do somewhat okay in The Lost Coast back in 2005.

like I (and ameratsu) already said.

Orange Box and Left 4 Dead should run.

Gears of War and Mass Effect both need a 2.4 GHz processor, but this is the minimum requirement. 90% chance that both games won't run smooth on minimum settings.

ATI Radeon 4670 has an AGP version, and you can run all of those games easily with it.

It costs $110

^ Still pointless without a processor upgrade. He'd be better off putting that $110 towards a x360.

Fixed.

It still depends on the CPU.

EDIT: Damn too late because I searched a price for a 3.2 GHz Intel processor ^^ (without luck by the way)