For whatever reason, nvidia didn't include the device IDs for anything above the GTX 960. To use a 980, you need to add a couple of lines to the .INF file (usually called nv4_dispi.inf)

1(under NVIDIA_Devices)
2%NVIDIA_DEV.13C0%           = Section008, PCI\VEN_10DE&DEV_13C0
3(under Strings)
4NVIDIA_DEV.13C0 = "NVIDIA GeForce GTX 980"

Thank you! I gave that a shot and it's still giving me the same old error: "This device is not working properly because Windows cannot load the drivers required for this device (Code 31)"

To expand upon this, it does list the device as a GTX 980 and I'm installing this manually through the device manager, if that helps.

Make sure you have also installed Extended Core (which is separate from Extended Kernel)

My god, I didn't realize the Extended Core is different from the Kernel, absolutely nowhere told me about that. I'm going to leave the instructions that I used to make this work down below just in case someone stumbles across this thread.

To get the 900 series working (probably the same for anything 500 series and up)

first, update everything (esp IE6)
then, update roll up 1
then, update roll up 2
INSTALL AUDIO HERE, EX CORE BREAKS INSTALLER FOR AUDIO
then, extended core
then, extended kernel
THEN, graphics driver is good to go!

Thank you so much for the help, I'm off to mess with the most OP W2K system I could think of.