I just put a creative x-fi extreme gamer in my pc and noticed that fps has dropped considerably in cod4

Before install: xp32 was getting average 100fps on most maps and vista64 up to 200fps inside building.
After install: xp32 now gets <50fps and vista64 about 70fps

I have the latest drivers for both os. (but no software for vista)

This is the only change made to the pc. Does anyone have any ideas?