Fps Help

I have no clue why this is happening, but it started to happen again. I have installed XP Proffesional on my 120 gig HD and I have a Gainward GF4 Ti4200 128mb video card. I have also installed MOHAA on my system and I don’t know what happens, but when I play the game, it just starts to lag bad out of the blue. It has nothing to do with my connection because my fps goes under 5 and sometimes up to like .8 and stuff like that. I have no clue what to do and I know it didn’t do this before. I have tried different drivers, tried reinstalling the games and I believe I have all updated drivers for all my things. Please help me because its annoying and I want to get it fixed.
-rahul ;]

System Specs:

P 3 800 MHZ
512MB SDRAM PC 133
120 gig HD XP Proffesional
Yamaha CD-R