I'm trying to solve a sound problem on someone else's computer, and it's driving me insane. Symptoms: No sound playback in Windows at all. The problem started out of nowhere, no one has any idea how it happened. It's an integrated sound card, and I'd have chalked it up to a dead sound card if it weren't for the fact that the audio still works on Dell's diagnostics tool accessed during boot-up. Integrated sound is enabled in BIOS. The sound device is recognized by Windows and shows up in Device Manager, but doesn't report any problems at all, it just won't play sound at all. Almost forgot to mention: Sigmatel HD audio, and yes, Microsoft UAA bus driver is installed too. Windows XP SP3. Things I've tried: Uninstalling and reinstalling all manner of drivers. Updated bios, reinstalled chipset drivers, reinstalled sound drivers about a hundred times. Thinking it was a driver conflict beyond my reckoning, I backed up all data and did a factory reformat. Still no sound. So, it can't be a dead card, since it plays the test song just fine in Dell diagnostics outside of Windows. But if a complete reformat can't fix this problem, what possibly could?