Had a similar problem... I'd accidentally deleted the Plug and Play Enumerator and no Audio Device was showing up despite the fact that all the drivers were reported as "Working Properly". This link tells you how to restore the PnP Enumerator.
http://www.annoyances.org/exec/forum/winxp/1070753464
Once the Enumerator was installed, Windows picked up the Audio Device immediately...solved my problem... might work for you