I found this and it fixed me -
I have pasted items 2 and 3 of ThomasK's solution - I jumped straight in at step 3 and it worked perfectly
Here's the solution that worked for me.
First check your System group in Device Manager and see if you see an
entry called "Plug and Play Software Enumerator." If you don't see it,
then I have the solution for you.
I remembered accidentally deleting Plug and Play Software Enumerator
from the System group in device manager. I reinstalled it, and
everything worked fine.
Here's how to reinstall it:
You'll need to find two files (try doing a Google Search)
Then Add New Hardware, System Device, and have disk. Choose swenum.
Install it. Reboot.
Voila. It should be fixed.
And, here are the basic steps:
Go to System in Control Panel, Hardware tab, Device Manager button.
Click the + in front of 'System devices' (near the bottom), and look for a line that says: Plug and Play Software Device Enumerator
This fix will only help if you are missing that line, or if you have a yellow exclamation point on that line! If you have that line, and there's no yellow exclamation point, then stop here and look elsewhere - you've got a different situation.
Okay, now that you've confirmed that you're missing the Plug and Play Software Enumerator, or that it's broken:
Make sure you have the following two files in Windows (do a search - they should be there):
You don't need to do anything with them, just make sure they're there.
1) Copy machine.inf from WINDOWS\inf to a temporary location
2) Edit the temporary copy of machine.inf - remove the line that says "ExcludeFromSelect=*", and save the file
3) in Control Panel, choose "Add Hardware"
at the 'Welcome to the Add Hardware Wizard' window - click Next
at the 'Add Hardware Wizard' window (when it finishes searching) - click 'Yes, I have already connected the hardware', then click Next
scroll to the bottom of the list of 'Installed hardware', and click on 'Add a new hardware device', then click Next
click 'Install the hardware that I manually select from a list (Advanced), then click Next
click 'Have Disk...', and browse to and select the edited machine.inf file
scroll down in the list of 'Common hardware types', and click on 'System devices', then click Next
under 'Manufacturer' on the left, select '(Standard system devices)'
under 'Model' on the right, select 'Plug and Play Software Device Enumerator'
Once the installation is finished, and the Device Manager shows the Plug and Play Software Device Enumerator under 'System devices', the audio should now work (no reboot required)