W2k looses site of graphics card

I am running a W2k pro pc with an on board graphics card. I have put a Voodo 3 graphics card in a PCI slot & disabled the on board in the bios. It detected the card as PNP & loaded the drivers. I re-booted & it was OK. I have since re-booted severaltimes & it was ok. I have left the pc for 48 hours & now i can’t get anything on the screen when the monitor is attached to the voodo card but it does come up on the on-board card.
It wants to then re-load drivers for the on-board card. In the control panel devices it thinks there is still a voodo card their ?? The bios settings are still as i left them ???
I have tried the card in a different slot & re-loaded the drivers & changedged the cmos battery & still no joy. Help.