Which - suite of PCmark testing are you running 06 or Vantage ?? - if running Vantage you need to realize your CPU is going to score lower because you are using an ATI GPU !! (yes that is correct the VANTAGE score will change significantly on the CPU score due to not using an NVIDIA based GPU that has Physx support !)
The CPU tests that should be testing the CPU only actually use the GPU rendered Physics processing to skew the results of the test - so systems with an ATI video card will score much lower CPU and overall tests than the same CPU using an Nvidia card even if that GPU is in reality weaker !