Old pc upgrade

For 130 bucks you can't really go wrong, assuming he's not looking to play crisis or anything. I'd say its worth the upgrade at that price. You could easily play WoW or something less graphic intensive on that build.

You'd be looking at 400+ to do a new budget build, assuming you have all the periferals

I took an old P4 3GHz with 1GB RAM, Win XP Pro and put it in an Antec 300 illusion case with a good PSU and a 9800 GTX+ in the PCIE x16 v1 slot it has. It gets about 80% of the performance I got with my 3GHz athlon 64x2, 4GB, Vista 64 system. Good enough to play most games at 1680x1050, medium-high settings.

I dont know what games you want to play or what resolution the monitor is so I have no idea if a 7900GT is going to be powerful enough to make it worthwhile.

I can say the CPU will not be that limiting of a factor if the motherboard has a PCIE x16 slot for a graphics card.

Well I mean he doesn't really play graphic intense games because the GPU is the limiting factor. I mean he's not going to be playing Crysis or Bioshock 2 but some relatively new games would be nice. I didn't know that the 9800GTX+ fit in a PCIE x16 I thought it needed a PCIE 2.0.

It will fit, the throughput is just not quite as fast. if you are confident the 7900 is powerful enough then it is a viable option. I think a 4670 might make more sense, its about the strongest cheap gaming card.