Hi jboy, welcome to the forum.
Not that we'll ever know now, but I wonder if you had a corrupted or otherwise faulty installation or update of Windows 7, whose problems might've been corrected by an uninstall, followed by a reinstall. . . or, if that didn't work, a System Restore to a restore point just prior to the loss of your sound.
Just a thought, in case the problem ever happens again.
But in any event, good for you for finding the solution that worked for your particular situation!