Radeon 5450 is a horrible card for gaming, its one of the cheapest card that no gamer should ever get, if not everyone. the performance is so horrible its probably better if you save the money and go with the built in graphics on either your CPU or MOBO.
summary: your GPU is SERIOUSLY bottlenecking your CPU power.
Dang! I didn't think it was that bad. I'm Building my own PC soon. Crossfire , Radeon 6950. That should get Good FPS?