It's a prebuilt one from PCWorld in the UK, got it in 2005 and it's pretty crap to say the least

(Can't check right now), but it has:
Nvidia 6200
512 ddr pc3200 ram
etc.
I have the case, keyboard, mouse, monitor, powersupply and the like but I was just hoping for a few suggestions on a new graphics card, ram and maybe motherboard (dd2 ram cheaper than ddr?)
Budget: < £150
I am not hoping for some uber just released hardware, just mid end (or whatever) to be able to play Guildwars and WoW with 'decent' fps, hopefully.