I'm pretty sure mine uses AGP, but that could be something entirely different.
Frankly, I'm a total newb when it comes to building computers.

AGP slots are otudated and not capable of decent performance.

Concentrate your efforts on a new motherboard, young padawan.

Except it is PCI-E. Anyway, doesn't matter, it's ♥♥♥♥ rad as ♥♥♥♥ and better than your face. Stop derailing ♥♥♥♥♥.

Okay, I'm not sure whether it's PCI or AGP. Where exactly would I find that out? I can't open the computer up, by the way.

Its a matter of finding the model of the PC, then.

Can you get on IRC? I'm tired of refreshing this topic.

Uh, sure.
Give me a second to connect.

So then, I got this all figured out thanks to THOR and some other people on other sites.
And just in time, too, as with the update of Garry's Mod, I can no longer run it.
So now I'll play the waiting game.
Thanks for the help, everyone