If it's a Voodoo1, then there's definitely another Video Card in that System (likely onboard Video)

The Voodoo1 is a 3D Only card, therefor it needs a 2D Video card (any).
Since the Problem you're describing comes from your Onboard / 2D Video card, the 3dfx plays no role in it.

Chances are, you need a proper Video Card driver for whatever you got as a 2D Card.

The Device Property page will list the Display adapter (if a Driver is installed), otherwise it may read "Standard VGA".
If you're not sure what Model/Chip it has, either consult the Motherboard manual or download and run Everest (or any other Hardware analysys Tool)