SIGMATEL STAC 92XX C-Major HD Audio Drivers on Windows 7

I've been upgrading a few of our PCs and Laptops with Windows 7 this evening and hit upon a problem with the SIGMATEL STAC 92XX C-Major HD Audio device that came with my Dell XPS M1330 laptop. A quick google confirmed I wasn't the only one having problems.

Since I have now solved the problem I thought I'd post it here on my blog as I'm sure it will be a popular search on Google in the coming months as the masses move to the new OS.

The symptom
Following a fresh install of Windows 7 (I haven't tried an in place upgrade as I just don't trust 'em !) the OS sees the Sigmatel device and reports it to be working, but the sound just doesn't work. Any attempt to download and install the latest Vista drivers also fails to cure the issue.

The fix Audio
Download the latest x32 or x64 (as appropriate for your computer) Vista driver from the Dell website and leave the EXE in a folder somewhere
Or get them direct from us, click for the 32 bit driver or for the 64 bit driver
Right click computer, and choose manage, then device manager. In the Sound, Video and Game controller group you will see a device called "Windows High Defintion" - delete this by selecting and pressing delete. Now having removed this device from your system you should run the Dell Sigmatel Driver EXE you downloaded previously
Your system will prompt for a restart upon install. When you restart you will get the reassuring sound of the Windows 7 start up tune and all will now be well !

Base System Device problem (Inspiron 1420)
http://ftp.us.dell.com/chipset/R141246.EXE

Hope this helps someone, took me an hour today to figure it out.