I NEEEEED HELP :<

I have a serious problem with crashing my fps in game. They are so unstable just since i formated (yesterday), before i had always 100 .

this is my computer (and i think is not even so bad):
- (CPU1) Intel® Pentium® 4 CPU 2.40GHz @ 2400MHz (Intel Corporation D845PESV mainboard)
- (RAM) 1GB, 689.32MB free (HDDs) 74.5GB, 69.3GB free
- (VGA1) NVIDIA GeForce 6600 GT (128MB), 1280x1024x32, 85Hz (OS) Microsoft Windows XP Professional, 45m 8s uptime, 11h 22m 11s uptime record

If anyone know what should i do plz write here.. :-( I will be very happy :)

EDIT: I already tried to reinstal graphic drivers.