any agp card will fit the mobo. And to check ur psu wattage just open the case and read what it says in the psu.
And I think that COD2 and all of the other new games have a minimum of 512mb ram, so it might work with what u have now, but not well. And also that cpu is quite old, so don't expect it to perform that well in the games.
But a new vid card and u should be able to play the games, but most likely with the lowest settings possible, and even then u might get low fps at some times.