We need more detail. My first response is - turn on the computer!
You could have
1) Your speakers disconnected or unplugged.
2) Broken speakers
3) Your volume control set to mute or low. Do you know how to bring up the volume control? If not, ask.
4) A driver problem. Bring up Device Manager and look for something with a yellow exclamation point next to it.
Did it ever provide sound? Are you using built-in speakers, headphones, external speakers? A little more detail and we can help you pin it down.
If you are using external speakers, try plugging them into an iPod (or something with better quality) and see if they play.