Computer Audio Stopped Working

Sometime in the last few days the sound on my wife’s laptop stopped working. She watched a show on a few days ago, and things were fine. Last night, no sound. I have tried watching youtube clips and other videos online with both Firefox and Internet Explorer. I tried playing a song through windows media player. No audio.

The only items recently installed were AVG and some windows updates. I uninstalled those items. Still no help.

Sound isn’t muted, volume is turned up. According to the device manager, the device is working and the driver is up to date. I also tried plugging in headphones - didn’t help.

I thought maybe the speakers were bad, but the windows start sound plays when windows first boots up. After that, nada.

It is a Sony Vaio runing Windows Vista Home Premium. We purchased it in Feb of this year.

Anyone have any ideas? I don’t know what to do.