My computer has no sound anymore
 

A couple days ago I was listening to NPR online and all of a sudden the sound cut out. For the past few days my computer has had no sound. I've tried restarting, but nothing happened. Everything is plugged in and the sound isn't on mute. Anybody have ideas on what happened?

I don't know if it matters, but shortly before the sound went out I downloaded a sketchy file over shareaza. It was a zip file. I deleted it without opening it, and virus and spyware scans I have run since then have come up clean.

Thanks in advance.