My sound on my Tosiba laptop has gone. Suggestions please!

Hi,

I'm a Laptop virgin, though I've been using the Public Library desk top computers for yuears. A number of things puzzle me about how the laptop seems to work, but practically and most urgently I've just lost the sound, so I cannot play music or dvds, which are the main things use it for. Its a great novelty visiting sites at will, what a thrill, but apparently I'm accumulating data on my 'Disc', because though I just go to sites and come off them I keep getting warnings of 'very low disc space', which I usually let the computer clean up when it volunteers to clear out stuff I don't use.
Would be so grateful to receive any vital or necessary low down on using laptops. Mine's a Tosiba.
See Ya
bromios7