If you are not hearing any sound, first check to see that your computer's volume is turned on. Volume control is accessed by left-clicking on the speaker icon on the Task Bar. This is usually located at the bottom of your computer screen:
Click on this sample sound to test your volume:
(Flash to come)
If you have external speakers, make sure they are plugged in, turned on (look for a power switch), and make sure volume is turned up to a suitable level. For advanced sound adjustments, right click on the speaker icon.