I can comiserate (maybe.) A system was updated with Windows ME and had onboard sound. The user had allowed windows update to update a driver.
You may not like the final fix, but I'll explain why we had to do that.
The WU sound driver was some VIA onboard sound driver. Issues ensued just like yours. After an initial try of SYSTEM RESTORE didn't fix it and downloading the drivers and installing them from the motherboard maker's web site didn't fix (it does most of the time), we disabled the onboard sound and used a 10 buck sound card.
This has occurred to many people and the story has been:
1. Install sound driver from maker and it's fixed.
2. Install sound driver of another version and that fixed it. Care must be taken NEVER to change or allow WU to update the sound driver. You don't want to know a high percentage do break it anyway in spite of warnings not to allow WU to update the sound driver...
3. Items 1 and 2 don't fix it and a 10 buck sound card fixes it. Yes, onboard sound is disabled...
4. Items 1 and 2 don't fix it and a Sound Blaster (from 35 to 200 buck) sound card fixes it. Yes, onboard sound is disabled...
I hope this gives you insight into fixing your issue.
Bob
I updated Windows and after updating, I lost sound in my games. They start off with sound, then they lose it.I did nothing else other than do Windows updates.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic