Shoutbox

What exactly have you tried?

Have you restarted the computer?
Have you unplugged your speakers and plugged them back in?
Have you tried plugging in headphones?
Have you check that the sound hasn't been muted?
Have you checked that the program you're using hasn't had the sound muted?
Have you check that your sound card is still selected as the output source for sound?
Have you installed the latest drivers for your sound card?