GeForce4 TI 4200 Fps drop

Hi, I own a MSI GeForce 4 ti t4200 and I dont know why but my cards seems to be working really bad since a couple of week. Well, I have huge fps drop in Counter-Strike, From 100 to 60 when 4 pple apprars in the screen. This thing happens in 640x480 to 1600x1200 resolution, the same drop. I’ve noticed too that my card wont drop If I turn de Vsync On but 60 fps is not enough for me. I’ve tryed to reformat, win2k, winXp, all detonators but still, I have this damn fps drop which should not happen. If someone know how I can fix this thing, please reply to this post.

System Config (actual)
msi board
512 mb ddr
msi gf4 ti 4200 128 mb
athlon xp 1800+
win2k and last detonator driver

wtf ?¿