I had a Radeon 4670 that I replaced, with an Nvidea GeForce gtx460.
Now My sound doesn't work. I figure it was a driver issue, so I installed the manufacturers recommended driver, but it still doesn't work.
What can I do to get audio working on my computer again?

Here's what lshw says about my audio device:

#lshw

...

*-multimedia

     description: Audio device

     product: MCP61 High Definition Audio

     vendor: NVIDIA Corporation

     physical id: 5

     bus info: pci@0000:00:05.0

     version: a2

     width: 32 bits

     clock: 66MHz

     capabilities: pm msi ht bus_master cap_list

     configuration: driver=snd_hda_intel latency=0 maxlatency=5 mingnt=2

     resources: irq:23 memory:fe028000-fe02bfff