Windows 7: Counter strike: Source - issues

After installing windows 7 onto my computer and wanting to play CS:S i realised that my FPS were averaging around the 100 mark. Its playable of course but, when i had my old OS (XP x86 SP3) i was averaging at around 250. I still have all the same hardware and theres nothing different in settings (Everything is maxed out)

I have a OC Q9400 @ 3.2GHz and a GTX 295

GPUz and TM states that load only reached 50% tops.



Does windows 7 limit loadings to playable FPS to save on energy? Ellaboration would be helpful thanks.