The problem
Do you come across this kind of problem that when your C- Media AC 97 Audio device doesn't work after you had done a system restore, and even if you've tried downloading different drivers, but it doesn't help. In BIOS onboard audio it's set to enabled. All the cables are correct...
The solution
First of all, make sure you have the correct drivers ready.
Then, go to Control Panel > Add/Remove and see if there's a listing for the C-Media audio... if it's there, run the unistaller.
Next, boot into Safe Mode and go to Device Manager... remove ALL listings for sound. Then reboot and see if Windows sorts it all out. Have the driver ready in case you need it....
Popular C-Media Audio Driver