There are no active mixer devices available

Struggling with this one.

What I have done;

Check the Device manage - no errors
Uninstalled the Realtek sound chip and installed the lastest drivers for this.

Have Check the BIOS - sound is enabled

The windows audio service is enabled to automatic within services.msc.

Even when I install a separate sound card I still have this problem.

This problem has occured twice now - when I have recoverd the computer. Oldish computer with recovery with service pacl 1(XP) - the sound is fine then and no problems, the sound suddenly stops when the full version of service pack 2 is installed from the microsoft update.

Obviously need SP2.

Any clues out there?