Set the card to your monitors refresh rate at that particular resolution.
That should keep it in the middle of your screen :)
-ilmore
Your problem is that the game is causing the card to switch to a different
refresh rate when in "3D mode". If you don't have a monitor that can
"remember" the different settings, then you need to ensure that the card
uses the same refresh rate in games as it does for your desktop.
I'm not sure how you do that on your Voodoo3, but on my Orchid Righteous
3dfx card there is a settings tab in the display properties which allows me
to choose the refresh rates at various resolutions.
HTH.