- Make sure this Monitor is not listed as "Unknown Monitor"

- If his Monitor is listed correctly, or at least a working substitude is used, try this :

> Set 16bit Mode in Display properties only (don't change Resolution)
> Reboot
> System should now boot in 640x480 16bit, with the V3 Display Driver loaded (the Windows fallback vga.drv is used anytime 640x480 16Colors is selected or induced by problems)
> from there on, Resolution should be able to be set as desired

If that doesn't work, re-install the Driver.

And finally, if that still doesn't work, uninstall all 3dfx Tools/Software, uninstall the 3dfx Card from the Device Manager, and Reboot into Safe Mode.
In Safe Mode, edit the registry (Execute > RegEdit) and delete all 3dfx entries related to Display Adapters/Settings.
Basically, all 3dfx entries can safely be deleted, as Windows by default only carries a few workaround Keys for a few, very old Games.
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Just make sure you have the right Driver for the right OS, since you didn't post those important details.

Note also, that V3-3500 requires a correct, regional Driver.
E.g. installing a Japanese Driver/Software for a US- V3-3500 won't work, neither will installing a US-Driver for a non-US V3-3500...

But that's the only catch I know of. Once that's being taken care of, all Win95/98/98SE/ME/2000 Systems should run without problems with the Card.