tiny voices said:
Chances are the GPU is just weak. It is a VERY bottom end card. My girlfriend used to have one in her computer before we upgraded her and even at 1600x1050 she had to run most newer games at low-medium to get more than 30-40fps.
15fps does sound a bit low for that resolution though. What are your CPU and GPU temps under load?
Gpu temp : 47c
Cpu temp : 50 c