I'm not sure if this is what you did, but rule #1... NEVER update drivers through Windows Update. Every time I've done this, without fail, it causes the device to stop working. After that, it's like pulling teeth to get the thing working again. If you haven't already installed all your emulators and games, I would almost suggest starting from scratch. If you didn't do the above then I think Dave's suggestions would be the best way to go.
If at all possible don't place a PCI card in the slot just below the AGP. Usually they share an IRQ, well, that's the way I remember it being anyway. Also, make sure if you have onboard sound you have it disabled in the BIOS.