915, 925, and (most) 945/955 boards won't work with the newer C2D/C2Qs. There were a number of second gen 945 boards that could handle C2D and some C2Qs. The older 65nm chips worked better, the newer 45nm chips might have issues. If you have a 965, 975, or P3x/p4x chipset then you should be able to handle any C2D/C2Q though even there there are some exceptions if my memory serves.
As mentioned above even with the C2Q 9550 it's below the minimum specs. You would honestly get better frame rates with a newer core series CPU, even if it's a lowly i3. C2Qs are simply really old now. You can run a program called CPUz to figure out what motherboard you have if you don't know.
http://www.cpuid.com/softwares/cpu-z.html