This seems to be a VERY common problem, there are threads all over the net, however very few have solutions that are meaningful. Tested a bunch of drivers (from Sony site and even updated sound drivers from Dell) and none worked. So far I have tried, restoring the drivers, deleting the drivers and re-installing the original ones off the Snow Leopard DVD (that use to work!), downloading the SigmaTel drivers directly off their site, updating bootcamp and running the KB835221.exe, a driver several other people had success with after installing. I spent several hours on the net looking for a compatiable driver, and alot of people ran into trouble with the SigmaTel High Definition Audio Codec when they upgraded to Vista. I have been told that windows might have automatically updated my original drivers with a new version that no longer works. It installs them, but immediately comes up with a conflict. I even deleted all of the drivers, let windows detect the new hardware, then I pointed it to the original audio drivers off the Snow Leopord install DVD. From there I have read every forum I have come across and downloaded various versions of the Sigma Tel drivers to no avail. :SigmaTel High Definition Audio Device Driver for SONY VGN-SZ440 This utility installs the originally shipped version of the SigmaTel High. I have tried restoring the drivers to a previous state but that did not work. It is having problems with the 'SigmaTel High Definifion Audio Codec'. I then went into my control panel and saw that there was a problem with my audio device. Until today, the machine has performed perfectly, however out of nowhere I noticed the sound stopped working. I am on a intel imac, running bootcamp 3.0 and windows XP. The program's installer files are commonly found as RoxioCentral36.exe, staceq.exe, sttray.exe or tinyuj2.exe etc. This PC software can be installed on 32-bit versions of Windows XP/Vista/7/8/10. This free program was originally developed by SigmaTel.

The following versions: 5.10 and 5.1 are the most frequently downloaded ones by the program users.

Hey guys, I have literally spent 3 hours trying to fix this sound problem. SigmaTel Audio is included in Multimedia Tools.

Sigmatel audio device drivers