Lies, there is a way to fix this. Jits is right.. your framerate is synching to your monitor refresh rate, thats why it stays at 75-85fps. If my geforce2 could turn vsync off, im pretty sure you guys can.
FOR QUAKE2 and DP, you have to type cl_maxfps 0 or cl_maxfps 200 or whatever before it will actually go any farther then your monitors refresh rate. This will cap your fps to whatever your card can handle or what you like. 0 is unlimited(not sure if this works for quake2 or not) And yes, when you go over your monitors refresh rate, horizontal tearing occurs.
My old geforce2 could pull about 150, but now my 6800GT pulls 1000fps at all times, so i cap it around 200fps.
It's not the nvidia drivers...
Hope this helps!