It shows "No audio output device is installed"on my Windows 7 system.

It probably is NOT a driver issue, but that's easy to check. Just do the following:

• Click Start, type Device Manager in the Search box, and press Enter
• Scroll down until you get to "Sound, video and game controllers" and double-click on that
• Click on each of the items in this category to open the item's "Properties" and look at the "Device Status"
• Just to be thorough, scroll up a little in the categories in Device Manager and see if there is a category named "Other devices" -- see the screenshot. If there is such a category, post back for further instructions

Although it's helpful to know that your High definition audio device is working properly, it's possible, especially given that you've just reinstalled Windows, that you actually have another hardware sound device in the computer and it is that device which is actually connected to your speakers.

Please answer ALL of the questions.

1. Do you have a laptop or a desktop/tower?
2. If you have a laptop, are you using its built-in speakers or are you using external speakers?
3. If you are using external speakers, for either a laptop or a desktop/tower, have you double-checked that they are powered on (most external speakers have a small LED that should be lit when powered on)?
4. If you are using external speakers, have you double-checked that they are connected to the proper jack on your computer?

When you were going through the suggestions offered by Bill Smithers, did you open the "Sound" applet? That looks like the screenshot at the end of this post, although you will likely have different icons showing. Open the Sound applet by right-clicking on the Sound icon on your Taskbar and selecting "Playback Devices." 5. What icons are shown in your Sound applet? 6. Which one has the green circle with the white check (like "Speakers" in the screenshot below)? 7. Do any of the icons have a red X? If so, which one(s)? 8. Do you have an icon that says "Speakers"? If this is NOT already marked with the green circle with white check, click on the icon to select it and then click the "Set default" button at the bottom of the window. 9. Right-click on each of the icons and select "Test." You should see the bar graph at the right of the icon turn green briefly, like this:

10. For each of the icons:

- Did you see the bar graph turn green briefly after you clicked Test?
- Did you hear any sound?

11. Assuming that you have a "Speakers" icon, right-click it and select Properties.
    • Does the drop-down list next to "Device usage" show "Use this device (enable)"? If not, change it so that is showing and then click OK
12. Click the "Levels" tab. Make sure that the slider at the top of the "Levels" window is somewhere in the middle and -- importantly -- that there is no red line through the speaker icon (see below). If there is a red line through the speaker, click it to remove the red line

Answers:

1. Desktop
2. External speakers (Altec Lansing)
3. Speakers are perfectly fit and play immersive sound when connected through smartphone by aux.
4. Yes, when everything was fine, I played sound through the speakers by connecting to the same audio jack (green colour) on the backside of cpu.

Unfortunately, the playback tab of sound menu shows:

”No audio devices are installed”.

That's the main issue.

I don't know what's wrong with the pc. If the sound card is not working or if the audio ports aren't working. Maybe I need to update the driver but I don't know how to do it. Or there's something wrong with the settings.

How to disable or adjust mt computer's sound. https://www.computerhope.com/issues/ch001481.htm

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OR:

Either do a system restore to before the problem:

http://www.sevenforums.com/tutorials/700-system-restore.html

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And/or go to your Laptop/Computer or Sound Card Manufacturer's website > look for the Drivers and Downloads Section > put in your Laptop/Computer or Sound Card Model Number > look for your Operating System > download and install the Audio, etc Drivers you find there.

I don't think this is a driver issue. When I check for driver updates automatically, it tells that you already have the latest drivers installed.