Computer Help

Alright, some of you guys know your stuff when it comes to computers, so I was wondering if I could get a little help. Lately, I have been bemoaning my rather old computer. However, I don't have the money to buy a new one any time soon. As such, I was wondering how viable it would be to just upgrade it in parts. Currently, I have a Gateway DX4200-UB101A.

Processor: AMD Phenom 8400 Triple-Core 2.10 GHz
Graphics: Integrated ATI Radeon HD 3200
Ram: 6.00 GB

I was thinking of upgrading the video card since it is pretty much crap. However, the processor is pretty much middle of the road as well. But if I upgrade the processor, I might need a new motherboard or cooling unit and what not.


Oh, also, I'd like to be able to play Witcher 2 on at least medium graphics and the upcoming SW:TOR.
Is this a laptop?
Nah, its my old desktop.