Supreme Commander vs XPS 420 & SigmaTel

[important]
this is a copy from my blogpost on my own website, hope this helps other people with the same problem.
to Dell Support, I hope you'll adopt this solution and get the updated driver on the support website! (in the right spot)

As so many people have found out: the default Dell SigmaTel drivers for the XPS 420 do not work in combination with Supreme Commander.

Many hours I spend looking for the solution and almost convinced myself of buying a seperate soundcard, with that there was a new problem that the frontpanel audio is not usable in combination with most of the soundcards. You should find a soundcard that works with the DELL C6173 Audio Cable, which you can find on eBay or buy at Dell spare parts. I found a blogpost from Ed Bott which solved my issue with Supreme Commander, copied content to keep it here for reference.\

Update 19-May-2008: In the comments, E.P. notes that Dell today released a new Sigmatel driver package,  . This one is identified as v.6.10.0.5866 and once again claims to be only for OptiPlex 740 models. The dialog box lists the same models as those shown below. I’ve successfully installed it on two different Dell systems now.

By and large, Dell’s driver repository works pretty well.

But on at least one score lately, it’s been failing, and I’m not sure why. Last week, Microsoft pushed out a new IDT audio driver via Windows Update. IDT is the company that bought SigmaTel, which makes a lot of the audio chips used on motherboard-based PC sound solutions.

So if you have a SigmaTel audio system, that IDT driver should have been for you. Except it didn’t work. On the one and only system where I installed that update here, it wiped out my audio completely. And a lot of Dell customers had the same experience, based on the uproar in the Dell Community message boards.

The solution, as it turned out, was simply to install the correct driver. But finding that driver was harder than I expected. For some reason, Dell is not linking its master SigmaTel driver file to the many PC models that use this chip.

For example, when I went to look for an updated audio driver for my XPS 420, I was offered driver version 6.10.0.5511, released in June 2007. But I knew better and used version 6.10.0.5515, released in February 2008. I’m sure it’s the right one, based on this installation screen that came up at the beginning of the setup process: 

The driver package I was offered, using Dell’s numbering scheme, is R157052. The driver I downloaded is R173209. It is a unified 32- and 64-bit driver package and in fact, it even applies to my Inspiron 530. How do I know that? Because when I look at the advanced system details report for the Inspiron 530 I see that it is a DXP061 model, which is listed in the Dimension section of the screen above. (Follow these instructions to see what model number you have.)

This driver also allows you to install Vista Service Pack 1 on a Dell system that would otherwise be blocked by the older SigmaTel driver. So, if you have any of the following Dell models, go get the R173209 update (or the more recent R182475 driver listed in the update at the top of this post):

Dimension/XPS: 5100, 5100C, 9100, C521, DC051, DM051, DM061, DV051 DXC051, DXC061, DXP051, DXP061, E521 XPS 420, XPS 710, XPS 720, DXG061

Optiplex: 210L, 740

Precision: 380, 290, 490, 690