If you are using speakers on a desktop computer, the first thing to try is to test your speakers on a different computer. If they still don;'t work, then it's time to replace them. If they do, then there a few things to do.
You would first have to test the speakers on a different audio port & see if that makes a difference. If it still doesn't work, the next few steps will also apply if you are using a notebook.
Check to make sure that the volume is all the way up and NOT set to mute.
After making any adjustments to the volume, try playing any media file & see if the media player volume is also correctly set (cranked up, NOT muted).
(*) In the event that it comes up with an error, read it: it might say something about not having a sound device installed. If it does, then you will have to download the audio drivers from the Manufacturer's website
(You will need to type in you computer's Service Tag in the website to skip to the downloads page where you would look for the Audio Drivers category); if not, see below.
If you have Windows Vista or Seven with either HD audio or HDMI-capable display, right-click on the volume icon near the system clock and choose Playback Devices.
Something like this should come up:
Make sure to select the CORRECT DEVICE. If your computer is connected to an HDTV, choose HDMI. If it's a notebook computer, choose Digital Output. Otherwise, select SPEAKERS as seen above.
If all else fails, you will have to uninstall then re-install the sound drivers.
In Windows 7 or Vista, click on start & type "Device Manager" in the Start Search
box and click on the Device Manager icon that appears in the results list
For Windows XP, Click on Start -> Control Panel -> System.
The System Properties window pops up; click on the "Hardware" tab then click on "Device Manager"
In the Device Manager window, open the Sound, video and game controllers.
Right-click on your audio device and choose "Uninstall"
When prompted, restart your computer. It should work after that. If it does not, it will provide an error message that will determine the actual cause of the problem. You may end up downloading the drivers as detailed in the (*) section above.
If the drivers will NOT install and says there is no compatible hardware, then the audio device has stopped working & will need to be replaced. Any other error would pertain to the operating system and would be a completely different issue.