My PC (vaio laptop)speakers won't work.?

I have a vaio laptop (pc windows) and the speakers are built in and one day i was in the middle of a video chat and i just couldn't hear any thing all of a sudden. I didn't press anything at all. I tried restarting, shutting down, and loggingof multible times and it won't work. But i can hear the chime when i first start uo my computer. But i can't here CDs DVDs or you tube videos or any thing else/ HELP