TNT2 VERTICAL SYNC

Ive just installed a RIVA TNT2 video card.
On the OpenGL control panel should I turn Vertical Sync on or off.

What does it do?

Thanks.

Vertical sync means that the video card will wait till the monitor is in a blanking interval when it writes to the screen(prevents tearing). However if you have an old monitor with really bad refresh rates, its going to kill your frame rate in games, so then i would turn off vsync. However if you get a refresh rate of 60 or above leave it on.

Thanks for your explanation.
Is there a Windows or OpenGL function that
I can use in my programs to sync redraw
functions with the monitor refresh rate
at runtime?

Yupp, there is an extension called EXT_swap_control (number 172 non-ARB @ http://oss.sgi.com/projects/ogl-sample/registry/ ) that swaps buffers on retrace.