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Hey IM going to Jump right away and say which of all the bottom troubleshooting i think it is. Look at the back of your soundcard, its got to go in the light green adapter. Next is that device listed as the default device or default communication. It must be on default device. So if for some reason the HDMI is default, you won't hear it. Can you play the sounds with Headphones? if you can, then you know 100 percent its the bad speakers.
Make sure that your computer and speakers are plugged in, have power and are turned on. If the speakers are plugged in but don't appear to have any power, plug them into a different outlet. Some speakers are self powered and use a USB cable to supply power. Make sure that the USB cable of your speakers is connected securely to the USB port of your computer.
2
Retest the sound. If you still don't have any sound, make sure the cable connecting the speakers to the computer (known as a 1/8-inch TRS cable) is plugged into the green audio output jack on the PC.
3
If you're using self-powered USB speakers, remove the USB cable and plug it into a different USB port. If you're using outlet-powered speakers and have a working set handy, replace the suspected non-working speakers with the working pair to test.
4
Navigate to the Microsoft Fix It troubleshooter (windows.Microsoft.com/en-US/windows/help/no-sound-in-windows) to automatically detect and fix sound playback or hardware problems. If that doesn't work, proceed with the next step.
5
If you have an add-on sound card and none of the hardware or software fixes helps, you may have to replace the sound card. If you use on-board sound, it will probably pay to purchase an inexpensive sound card rather than a new motherboard. Check the system BIOS to determine whether you have inadvertently disabled your on-board sound.
6
Navigate to the "Start" menu and select the "Control Panel" and "Sounds and Audio Devices." Then click the "Volume" tab. If everything is grayed out, proceed to Step 7. If the "Mute" box is checked, uncheck it. In "Device Volume," make sure that your volume level is set to a comfortable volume level for your speakers.
7
Click the "Sounds" tab. Under "Sound Scheme," determine whether "No Sounds" is selected. If it is, click "Sound Schemes." A drop-down list will appear. Select "Windows Default" as the scheme. To test your sound now, click on a sound listed below the "Program Events" window. The sounds will be indicated by a small "Speaker" icon located next to them. Left-click the sound once, then click the "Play" button. If you still don't hear sound, proceed with the next step.
8
Click the "Audio" tab. Under the "Sound Playback" option, make sure your sound card is selected as the default playback device. Usually, only one device appears here, unless you have multiple playback devices installed.
9
If everything is grayed out, you either do not have a playback device installed or your drivers are corrupted and need to be replaced. Drivers help hardware and software function together. Fix this by reinstalling the appropriate drivers. Do this by navigating to the "Start" menu and right-clicking "Computer." Then select "Properties" from the drop-down menu. Click the "Hardware" tab and then click the "Device Manager" button. The Device Manager will open.
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Look for either a red X or a yellow question mark listed under "Sound, Video, and Game Controllers." If a red X appears, right-click the device with the X and select "Enable" from the pop-up menu. Test your sound at this point. If a yellow question mark appears, right-click the device, click "Properties" from the pop-up menu, and then click the "Driver" tab on the window that appears. Next, click the "Roll Back Driver" button to roll back to the previous drivers that were functioning correctly. Restart your computer when prompted.
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Read more: How to Troubleshoot No Sound From Computer Speakers | eHow.com http://www.ehow.com/how_4616823_troubleshoot-no-sound-computer-speakers.html#ixzz1dKrUoq3p
Thanks
Rhos Barnes, MCSE, MCPI, CCNA
thepctechguys.com