Upgrading old PC for son

hi guys i have an IBM ThinkCentre M/T 9210-KMV S/N L3K3096 it has a pentium 4 at 3ghz and 1gb of ram, i dont have the money to buy a whole new system so please dont suggest that i do, the computer runs fable lost chapters and so on, my son wants to know if it can run call of duty 4 thats all hes wanted for a while now, the computer does not have an agp slot which is very unusual what way could i upgrade the PC so it can run call of duty 4? my son doesnt mind playing at very low graphics

thanks

If 1024 x 768 normal settings is not too low just hit a cheapo 880G with HD 4250 integrated video/X3 + 2GB combo and u set for anything really - add a HD 6850 if his gaming needs ramp up (with a PSU upgrade hehe)

im getting a decent PC for him next year when sandy bridge and the bulldozers come out as he is taking I.T next year, the thing is his friends have quite a few LANs and he said hes missing out, i mean his friend has a pentium 4 and a radeon 9600 and it can play call of duty 4. thats why i just wanted to upgrade this old thing so he could play the game, i wanted to spend like $50, i think it has a PCI slot so maybe he could get an old graphics card? i could maybe get an extra gig of ram?

will this PCI card run call of duty 4? 128 MB ATI Radeon 9200 PCI Video Graphics Card, is this PCI card better than the 9200?

256MB NVidia Geforce FX5500 PCI Video Graphic Card DVI

i know but his PC has to last him around 6-7 years and he will be using cpu intensive programs, not just gaming, he will use solid works, auto cad, photoshop etc so i want to get him something decent at the time, so i just want to know will that PCI card run call of duty 4?