Home-made gaming PC (pretty modest, don't get any ideas), running Win XP (yeah, I know, but it's fine by me), using old-ish AMD dual core on an AM2 socket. It's connected via HDMI (through a DVI/HDMI converter) to a plasma TV, and via S/PDIF to a home theater amplifier. The TV is itself connected for sound to the home theater via an optical cable, which is rarely used (more about that below).
I took out the old 9600 graphics card and replaced it with a new GTX 560. The installation required the manufacturer-provided CD to install some drivers. Fine, I did that. Then I downloaded and installed the latest GeForce driver from NVidia.
This computer has and old Audigy sound card, without the breakout box. I use it because it works, and because I managed to get true 5.1 audio from its digital output to my home theater over the S/PDIF cable. 5.1 normally works only over the analog outputs; however, I installed some software (can't remember the name right now) that encodes the sound on the CPU in real time and sends it out over S/PDIF as 5.1. Everything worked perfect.
Now here's the thing: after finishing all chores related to the GTX 560, the Audigy card disappeared from the settings. I cannot select it as an audio output at the OS level, and sure enough there's no sound coming out of it.
However, the GTX 560 now acts as a sound device. It's sending out sound to the TV via DVI/HDMI. I could route the sound through the TV to the amplifier, no problem. But the thing is, it doesn't seem like the 5.1 surround works correctly. I tested some games (Portal, Civ V, Moonbase, Spore) and the front / rear separation doesn't seem to work; it's as if the rear speakers are only used for echo and ambience. It's like the Audigy over S/PDIF before I installed the real-time sound encoding software.
In Control Panel, I configured the speakers as 5.1, but it didn't help.
Two questions:
What could cause the disappearance of the Audigy card? Could the Gigabyte installer be so nasty as to remove the drivers for the Audigy?
I could live with the GTX 560 as a sound card, in fact I would prefer it, provided that I re-enable true 5.1 with front / rear separation for the games. Any suggestions?