Go to the link below and click on the "?" to the left of "Where did my Sounds go?" to expand it and you'll find several possible fixes.
Also try this:
Go to Start > Run, and type in: services.msc.
A window will pop up with a list of services. Scroll down to Windows Audio. Right-click
and click on Properties.
Make sure that “Startup type” is set to automatic. Also, make sure, under “Service
status,” start is selected.