Yeah the problem is you say you gave your son your computer and it's newer...well newer does not tell us anything. Anything between 1yr and 10yrs old could be what your referring to as newer, and without a good video card, your not going to be able to play that game.
We need to know what cpu, power supply, memory, etc it has to be able to suggest anything to you.
The PS3 was not sarcasm, it was a real suggestion. If he already has a PS3 and a Xbox, why on Earth would he want to play it on a older pc??? Makes no sense to me, take the game back and get the PS3 version.