Windows Vista audio problems after sp1

I installed sp1 on my Vista Ultimate laptop last week (Sony Vaio VGN-FZ290 laptop). Like many others, I lost my audio. I tried all the recommended fixes (installing latest drivers, reinstalling drivers, etc.). Nothing brings back the audio. Yet all indications are that my SigmaTel HD audio device is working properly. When I test for sounds, I get the "failed to play test tone," error message. I have also lost Media player, and Media Center.
I contacted Sony technical support. They suggested that I download an older SigmaTel audio driver. I installed it; no help. Since I have tried all the recommended fixes and the audio systems seem to be OK, can the problem be somewhere else?
Does anyone have any suggestions. Thanks.

 

I found the following on a Dell support forum concerning SigmaTel drivers and Vista's SP1:
1. You can uninstall the Sigmatel Driver, reboot, let VISTA install the sound driver and then download and install SP1, or;
2. You can uninstall the Sigmatel Driver, reboot, download SP1 and install, then I believe you can uninstall the VISTA driver, download the Sigmatel Driver and reinstall that, or;
3. You can try downloading the full SP1 434mb file, install it and if your sound drivers fail just reinstall at that time, or;
4. You can wait patiently as Microsoft is aware, Dell is aware and it appears they are working on a solution. Some people are not getting SP1 until Mid-April, so you would not be the only one waiting. Then when it's fixed, you will receive the SP1 via Windows Update.

I haven't tried it so I can't offer any assurances it will work.

A lot of new Dells are having the same problem with SigmaTel drivers and SP1.

 

Waiting. . .

Thanks for your help.
I tried suggestions 1-3. I guess I have to wait patiently for this problem to be addressed. What next with Vista?????