No Boot Device Found
Instead of starting Windows, the computer shows a message like "No boot device found" or "Operating system not found" — a plain text error rather than the usual Windows logo.
Quick answer: This message means the computer can't find a drive to start Windows from — most often because the drive has failed, is no longer detected, or a USB drive is plugged in and being read instead. Remove any USB drives and restart once; if the message persists, the drive itself needs checking before anything else.
Likely causes
- The hard drive or SSD has failed or is no longer being detected
- A boot order or BIOS setting has changed, sometimes after a power outage or hardware change
- The drive's connection cable has come loose (desktops) or the drive itself has failed (laptops)
- The drive's boot configuration has become corrupted
What you can safely check yourself
- Restart the computer once or twice in case it was a one-off glitch
- Check whether a USB drive or disc is plugged in and being read as the boot device instead — remove it and try again
- For desktops, if you're comfortable opening the case, check the drive's cables haven't come loose
If this message appeared alongside unusual noises from the drive, or the computer has been dropped or knocked recently, treat it as a likely drive failure and avoid restarting repeatedly — that can make data recovery harder.
When it needs a proper look
If the message persists after a restart and there's no USB drive involved, this usually means the drive itself has failed or is no longer being detected properly — that needs diagnosis, and if there are files on it that matter, data recovery should be assessed before anything else is attempted.