There are two possible scenarios;

Scenario One
In Sounds and Audio Devices you are told there is "No Audio Device"
In Device Manager your Audio Device is "Working Properly" and
You DO have "Plug and Play Software Device Enumerator" listed under System Devices

Carry out the following steps;
Copy C:\WINDOWS\inf\machine.inf to a temporary location
Edit your copy of machine.inf in Notepad
Remove line 20 (ExcludeFromSelect=*)
Right-click “Plug and Play Software Device Enumerator” and click “Update Driver”
Choose “Install from a list or specific location (Advanced)” and click Next
Choose “Don’t search. I will choose the driver to install” and click Next
Click “Have Disk”
Browse to the location of your copy of machine.inf and click OK
Select “Plug and Play Software Device Enumerator” and click Next
Wait for the software to install then click Finish

Scenario Two
In Sounds and Audio Devices you are told there is "No Audio Device"
In Device Manager your Audio Device is "Working Properly" and
You DON’T have "Plug and Play Software Device Enumerator" listed under System Devices

Carry out the following steps;
Copy C:\WINDOWS\inf\machine.inf to a temporary location
Edit your copy of machine.inf in Notepad
Remove line 20 (ExcludeFromSelect=*)
Go to the Control Panel and run “Add Hardware”
When the Add Hardware Wizard appears, click Next
Wait for it to search for new hardware
Choose Yes, I have already connected the hardware and click Next
Scroll all the way down and select “Add a new hardware device”, click Next
Choose “Install the hardware that I manually select from a list (Advanced)”, click Next
Select “Show All Devices” and click Next
Click “Have Disk”
Browse to the location of your copy of machine.inf and click OK
Under Model, select “Plug and Play Software Device Enumerator”, click Next
To start installing the drivers, click Next
Wait for the software to install then click Finish

Your audio device should now be recognised in Sounds and Audio Devices.

SOURCE: http://www.softwaretipsandtricks.com...roperly-4.html