Well the reason the games don't work is because DirectX is having a problem with the sound device "missing". Try updating your DirectX to the latest version, and that might at least let you play games (though with no sound).

But I don't know why the sound device isn't starting. You say it is normal in Device Manager? Are you sure it is there?

You could try Killerrabbit's suggestion of reinstalling Windows, and that would probably fix it (you can reinstall without losing files), but I don't think you need to unless this is a major annoyance. Also try updating or reinstalling the sound driver and see if that makes a difference.