Well you can just google the computer you bought if it's a brand name. I've never heard of a 7500 LE so I think I'll assume it's a 7300 LE, at which point it will in fact play Call of Duty 2, although not very well, if you only want to play Call of Duty 2 and nothing else, a 7600GT upgrade would be a good selection, if you would like to play future games and more intensive games, then I think a 7900GT or higher is in order.
Intel C2D e6600 @ 3.6Ghz
BFG 8800GTS 630/1000
Seagate 360GB and 160GB SATA II 7200 RPM
Cooler Master iGreen 500w Power Supply