Are they built into a laptop? If so, I'm not sure how to help you. If they're the type that are on your computer's monitor (screen), find the cable that runs off of them, the jack will usually be green. Plug the jack into a CD or Mp3 player and try to play music through them. If this doesn't work, then the speakers are probably toast. If this does work, let us know so we can provide further info.
As Peccavi said, it may be a volume problem as well. There's usually a volume control applet on the taskbar near your clock that you can use to adjust the volume as well.
Make sure that the mute isn't on, this is a common problem.
Ryeguy, January 2009
