Wow that isn't good eh? and seems I have to agree with Winuser in that the network card must be faulty and if it is the GPU then I think I mentioned before they usually soldered into the board unless the machine you have got has a removable one. That is a fair bit of work to do though.

Have you run any GPU tests on the machine yet? If not try this http://www.ozone3d.net/benchmarks/fur/ and it might be worth watching this first How to your GPU - YouTube - on another machine of course.