The computer I'm typing on was a store-bought HP... yeh, I wasted money on it. It's got a P4 2.8GHz, 7600GT (upgraded from FX5200), 1.5GB DDR400 RAM (upgraded from 512MB), 120GB IDE hard drive and some ASUS Oxford motherboard. It's alright for older games (since I'm restricted to 1600x1200 with my old, 15" CRT), but I tried running World in Conflict... it was alright, but tended to lag.
Now I know a little about computers, I got a custom-build from a smaller shop... I'd of built it myself, but my dad's not too keen on letting me mess around with $AU1700. Anyways, this one's got a E8400, ASUS P5Q-SE/R, 4GB DDR2 800 RAM, Asus 9800GTX+ 512MB VRAM, 500GB SATA hard drive, along with a case and 500W power supply, a 21.5" monitor, a Microsoft keyboard/mouse (what, I like them) and headset with mic, so I can finally talk during TF2.