What should I do with my ASUS laptop(don't have sound at all, but sometimes do)?

I have an ASUS F3Sg laptop but two day ago it didn't have sound, even at the starting ASUS logo and sound. Yesterday it worked well, had sound perfectly but today it doesn't have sound but there is no problem with the blasters because it also has no sound on the headphone :'( What should I do to fix this problem? :S