Texas Cud-- This is one way to check if your speakers are okay:

Unplug the cable from the back of the computer, and insert the stereo plug into the headphone jack of a Walkman, Discman or FM radio and play music. If the speakers are ON and working and the cable is good, you should hear the music from the walkman on the speakers.

If your speakers check out okay, then maybe it is your sound card??