There's two things that can make an older card stop working: An incompatible or conflicting IRQ address, or an incorrectly set COM port.
Did the Viper work
on the same machine before you put in the new card? Or is the Viper the card you've added to the system? If you moved the Viper from one slot to another to make room for the GeForce, the Viper might not work, because it wants to stay in the old slot, and if it's being added, it needs to know what slot it's in.
Take a look at the Viper… if it has jumpers for different IRQ numbers and different COM port numbers, that’s probably what’s wrong. Nowadays, instead of COM ports, these are called PCI slots… And older cards need to know what slot they're in to function correctly, even if they claim to be PnP.
So did you move the Viper, or is it being added?
And IRQ #s... Windows can put multiple devices on the same IRQ # without having a conflict, so it's a little hard to figure out. You have to use the BIOS, sometimes, to see if two devices are on the same number. Old diamond cards like to be on IRQ 5 or 7 , If I remember. (I had a Diamond card, long ago...)
For my own dual-monitor setup, I use my GeForce plus the card built into the motherboard, but I don't plug two monitors in too often.
See if the COM theory is correct, then worry about the IRQs...
If you want, you can IM me at AIM: ZImperial1 or MSN:
GrandAdmThrawn@msn.com