The little latch on the PSU's pci plugs were offcentre so that they would be in the middle if you used the little two pin plug hanging off it to make it a eight pin plug. Didn't know if that was okay so I just used what came with the gpu.
But everything is working great now, thanks for your help. I have a new question now though, and that's about what wireless card I should get.
Unfortunately I can't get wired internet to my setup (unless I can get it through a phone jack?) so I need to buy a wireless card. Do you guys have any suggestions for specific models or brands? What features should I be looking for to determine whether a product is high quality? What data rate would you recommend?