First, look on the bottom of your screen next to where the clock is in the right hand corner. There are small icons that open virus and other software that runs in the background. One should look like a silver, round thing. It is spoused to be a speaker. Double click on it and check to see if your sound somehow got muted. If so, uncheck the boxes.
Make sure no one put headphones on that overides the speakers.
The next easiest thing to do is to turn off your computer, unplug your speakers and restart without them on. Shut down again and plug the speakers back in. If there is still nothing, it could be that your sound card driver got corrupted or changed with a recent update of windows.
After that, go to Windows update website and set the update finder so that you can choose what gets downloaded. You would want to look for hardware updates.
From here, things get a llittle more complicated, so if you need help, try to find someone who can help. Your sound card is what controls sound on your computer. A driver is just software that controls the sound card.
The simplest place to find out about all the devices in and on your computer is in the control panel in the system folder. Depending on how you have Windows set, when you open your control panel, you either see the "classic or category view." See pic below. Choose classic view that appears on left upper side of the screen.
The folders are listed alphabetically, so look for the system folder. There are red arrows inserted next to sound folder and system. Double click on the system folder and then click the hardware tab on top. Open the device manager. You will see a list of things like the one on the right in the pic below.
The + sign next to devices opens the list. If you see and exclamation point, that means that the device has a problem. If you see a red X, that means it is disabled. You will see sound, video and game controllers listed alphabetcially. Click the plus sign. The list of devices opens. You can check the driver and function of each device by double clicking on it. Remember, you are in the controller area, so speakers won't be listed here.
Look at the list you opened for something that says digital sound. When you double click on the sound card, it will tell you if it is working properly. It should say something specific, not generic stuff. The driver tab on top will tell you when the last driver was installed.
If it is new, that is probably the issue. If not, it may be corrupted. Click update driver and go on internet to find a better one.
If none of that works, click the system devices tab and look for speakers. Go through the same list of checks. You can unplug speakers from the computer and just use the little speaker inside the computer to see if the problem could be the speakers themselves.
Last but most likely to cause problems is to remove your sound card and reinstall it. The problem here could be that windows hardware setup won't find it or the right driver and you won't have sound at all. Most sound card manufacturers have free driver updates that you can download, but it is critical that you know the name and version of your sound card to get the right one. I hope this helps, leave comments if you need further assistance.