It can be down to more than just CPU or GPU. The CPU isn't the most up to date, but shouldn't struggle too much. If you wouldn't mind going into more depth about your system it would help. Also you could go about updating your drivers.
intel core2duo e7300@ 2.66 ghz
4gb ddr2 ram
window 7(32 bit)
gigabyte 945GCM-S2L( PCI-Express)
Monitor-Samsung Syncaster S20B300 (1600*900).
Corsair CMPSU-430CXV2UK 430 Watts PSU(28A at +12V rail, 80+ certified).
graphic card-HIS hd 7750 ddr5,1gb.
will my cpu or card bottleneck?