Before I start this post off I just want to let you guys know, I'm looking for a pre-made build, I say this because I know a lot of people will just turn around and tell me to go and just build it myself. Simply put, I don't want to build it myself, unless there is a video tutorial or a really in-depth text tutorial telling me exactly what to do and where to put what part, with the exact same parts that I would have for my build. Yes, I am that much of a noob, and chances are I'll probably break something if I didn't know exactly what to do with it.

Budget: 400-550GBP ($600-850USD)
As I said before, I'll be gaming on this rig so I'll need a good graphics card and processor. Preferably at least a 500GB HDD. Monitor preferred but not 100% necessary, same goes with keyboard and mouse. At least Windows 7 included, not really bothered about the version of Windows 7.

If there is anything else that would make finding the PC easier, maybe I missed something, please let me know and I'll update the topic. Thanks