Can anyone please tell me how to restore the audio?Try doing a Windows "System Restore," under Start/All Programs/Accessories/System Tools/System Restore (or else enter "System Restore" into the "Search Programs and Files" box under the Start button).
Choose the most recent restore date which is offered that is prior to when the "no audio devices installed" problem arose.
Doing that will not affect your music files, data files, emails, etc., but will undo any Windows updates, and possibly program updates or installations, that have been performed subsequent to the restore date. Those updates would therefore have to be repeated.
If the System Restore doesn't fix the problem it can be reversed to the present date, which would eliminate the need to repeat the Windows or program updates that may have occurred between the two dates.
Best regards,
-- Al