If there is no sound coming from your computer and you see a red cross on the volume icon in the taskbar with the warning "No audio output device is installed", the problem is usually a faulty audio driver or a disabled device. The good news: in most cases it is fixed in a few minutes. Here are the step-by-step methods.
Common Causes of the Error
Windows shows this warning when it cannot detect an audio output device. The most common causes are: a corrupt or missing audio driver (especially after a Windows update), the audio device being accidentally disabled, a stopped Windows Audio service, and rarely a physical connection or hardware issue.
Solution 1: Run the Audio Troubleshooter
The fastest start: right-click the volume icon in the taskbar and choose Troubleshoot sound problems, or go to Settings > System > Troubleshoot > Other troubleshooters > Audio. This tool can automatically fix disabled devices and simple driver problems.
Solution 2: Enable the Disabled Device
Go to Settings > System > Sound. If the output device is not visible, right-click the taskbar icon and open Sound settings, find your speaker under the All sound devices section, and if it is disabled choose Allow / Enable. In Device Manager you can also right-click the greyed-out/arrowed device under Sound, video and game controllers and choose Enable device.
Solution 3: Update or Reinstall the Audio Driver
Open Device Manager > Sound, video and game controllers. Right-click your audio device (usually Realtek Audio) and choose Update driver. If the problem started after an update, try Roll Back Driver. If that does not help, right-click the device and choose Uninstall device, then restart the computer; Windows will reinstall the driver automatically. For the most stable result, install the latest audio driver from your motherboard/laptop manufacturer's website.
Solution 4: Check the Windows Audio Services
Open Win + R > services.msc. Make sure the Windows Audio and Windows Audio Endpoint Builder services are Running and their Startup type is Automatic. If they are stopped, right-click and choose Start.
Solution 5: Repair System Files
If you suspect general corruption, run in an administrator Terminal:
sfc /scannow
DISM /Online /Cleanup-Image /RestoreHealth
When the process finishes, restart and test the sound.
Frequently Asked Questions (FAQ)
The sound problem started after an update, why?
A Windows update sometimes installs a generic driver that is incompatible with your existing audio driver. Rolling back the driver or installing the manufacturer's up-to-date driver fixes it.
I get sound when I plug in headphones but not from the speakers, what should I do?
Check in the sound settings that the correct output device is selected. If the speaker device is disabled, enable it; if the driver is out of date, update it.
No audio device appears at all, is the hardware faulty?
It is usually driver-related. Uninstall the device and restart; if it still does not appear, check in the BIOS that the onboard audio is enabled.
Conclusion
The "No audio output device is installed" error is mostly caused by a driver issue or a disabled device. Running the troubleshooter, enabling the device, and reinstalling the audio driver resolve almost all cases. Checking the services and running SFC/DISM also clears up stubborn situations.