Originally Posted by blacklabelsktr2

Not sure if this would work (it should work in 32bit mode for sure), but try fixing the sound this way. Download one of the original packs:
Old X3100 pack: http://www.box.net/shared/5dxqfrx5oz <-this one for you
Old NVIDIA pack: http://www.box.net/shared/xhi6evrq1s

1. You should see a VoodooHDA.kext. Drag it into Kext Helper b7 (download it if you dont have it)
2. Open folder called VoodooHDAHelper, drag the Voodoo HDA Helper program into your Utilities
3. Copy the folder VoodooHDA to Your_OS_X_disk/Library/
4. Add application Voodoo HDA Helper to list of login items in
System Preferences > Accounts > Login Items
5. Double click and install VoodooHDA.prefPane.

This is how I fixed my sound multiple times, works for me in 32 bit, I haven't tried 64 yet. Let me know if it works.