Alright, I will try and make this as simple as possible. I am assuming you run windows, not mac or linux. Make sure you don't have the sound muted on your computer or left headphones plugged in.
Go to START > Control Panel > Sound > Playback tab
Alright, with the playback tab selected, does are there ANY speakers listed? If yes, click on the speaker listed so it is highlighted, and then hit the CONFIGURE button that is below. Run a test, and make SURE that you have not accidentally muted the sound (BIG issue, my grandmother thought she broke her speakers when she had muted them and forgot about it). Did the test work? Did you hear anything? Turn the sound up if need be and try again if not.
Let us know of that works or not, if so, yay! If not, more troubleshooting to come!