<<...it says no audio device is installed...>>
What is "it"...where/when does that message appear?
If Device Manager reflects proper install of audio...and you receive that message, then I'd have to say that's a hardware problem.
Please download MiniToolBox
, save it to your desktop and run it.
Checkmark the following checkboxes:
List last 10 Event Viewer log
List Installed Programs
List Users, Partitions and Memory size.
and paste the content into your next post.
Also...please Publish a Snapshot using Speccy - http://www.bleepingcomputer.com/forums/topic323892.html/page__p__1797792#entry1797792
Have you run the Sound Troubleshooter in Vista?
Have you tried MS FixIt, http://support.microsoft.com/mats/AudioPlayback/