Failed to play test tone Solved! This worked for me.
If you have gone crazy and re-installed all the sound drivers, set to default/enabled and disabled all your sound devices, did a system restore and that still didn't help. Try This!!
Download > Link Removed(this link is for x64 based systems)
This installed a Hot Fix on my PC that was needed to do a proper windows update!
Then try Updating Your Windows and see if Windows 7 Service Pack 1 comes up.
I needed this on my PC. After this was installed and my PC was restarted Voila! I had Sound!
If your Windows Update does not...