Here's what I have, and here's what fixed it.
Gateway Media Center GM 5048, Windows XP Media Center, service pack 2.
Intel Pentium 930 processor
I restored the system.
I had no audio devices recognized, "Sound" said no audio device, the whole "Audio" tab was greyed out and I couldn't enable anything. My card was enabled in BIOS, Windows Audio was started and enabled, and my Plug and Play Emulator was up to date. I was just getting ready to throw the computer out the window when I tried Gateway's online live chat tech support, and they gave me a driver that made it work! This driver wasn't even labeled for my computer but it worked. Here's the link:
http://support.gateway.com/support/d...&uid=153742017
I hope this helps someone out there!