What version of Windows, including service pack (right-click My Computer > Properties)
What happened just before the problem arose?
Click Start > Run > services.msc > OK
Scroll down to "Windows Audio"
The Windows Audio service should be Started and its "Startup type" should be "Automatic." If it is not started, double-click on the entry and click the Start button. If this fails to start the service and instead generates an error message, the file for the Audio Service may have become corrupt or deleted (although this file should be protected by Windows File Protection).
Search your system drive (probably C:) for
audiosrv.dl (that's only one L)
Make sure to look in "System folders," "Hidden files and folders," and "Subfolders."
You should find audiosrv.dll (with two Ls) in C:\Windows\system32.
If it's not there, it should be in C:\Windows\ServicePackFiles\i386
If it's not there either, do you have a file named audiosrv.dl_ in C:\i386?