frame rate drops greatly every 10 seconds

[OTWarrior]

I have just installed windows 64 and all of the drivers (motherboard, sound
card, directx, windows updates, graphics card, keyboard utility) however when
i try to play any 3d game, the frame rate keeps dropping every 10 seconds,
for example, when I was in the main menu of the TF2 beta, the frame rate was
300 (as I had yet to change the resolution) and every few second it would
shoot down to 70.

(yes they are high frame rates, but yopu get the idea)

different example, Bioshock runs at 30 fps normally, and drops down to 2 every 10 seconds

I have tried disabling all background processes that I do not need, but it
makes no difference.

Any ideas?

[OTWarrior]

these are the specific system specs:

hardware
******
Bios version - 2.2 061807
motherboard - p6n sli-fi
video card - ati radeon x800 pro
processor - intel e6850
4 gbs ram (ddr2)
sound blaster x-fi fatality gamer
Razer copperhead mouse (blue)
Microsoft reclusa usb keyboard
Belkin Nostromo n52 speedpad
5.1 surround sound speakers (by creative)


operating system
******
windows professional 64 bit
SP2
directx 9c


drivers installed
*******
7-9_xp64_dd_ccc_enu_52443.exe (Video card)
NVIDIA_C55_Chipset_x64_MB.zip (motherboard)