Cheap computers

aiguyaiguy asked: I am looking to buy a new computer for use as a PVR and Gaming system on my 42″ HD TV. I know both Alienware and Polywell have systems now that look like stereo components and will fit nicely in my rack. Both systems are over $5000 configured the way I’d like them. [...]

anon asked: I was thinking of building my own pc, but im not 100% sure on all the parts i would need. So if you could list the parts i would need, and a resonable place to get them from. Also i was looking at spending around £400 with or without peripherals.