Sound Not Working

have you rebooted yet?

Yes.

Start->Settings->Control Panel->Sounds and Audio Devices. Make sure all the settings correspond with your equipment and needs. Be sure to click the Audio tab and confirm the correct playback device is selected. Under the Volume tab, click the Advanced button in the Speaker setting section and confirm things are correct there.

Close and reboot the computer before testing to see if that fixes it.

Plug in an earphone to check if the speaker had not gone south on you.

I have same problem,
I formatted my computer and installed the sound drivers.But no help !