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The “An operating system wasn’t found. Try disconnecting any drives that don’t contain an operating system” message does not mean you must format the PC or that your files are gone. It means the computer did not find a usable startup path. First remove unnecessary external drives, then check whether the internal Windows drive appears in BIOS/UEFI and whether the firmware is trying to boot from the right device. If the drive is missing or may be failing, avoid repair steps that write to it until important files are protected.
What the error means
The computer has not located a usable way to start Windows. That can happen because firmware cannot detect the storage drive, the wrong drive or boot entry is selected, or Windows boot information or partition state is damaged. The message alone does not establish which cause applies, prove that the drive has failed, or mean Windows must be reinstalled. Microsoft Learn community discussions from 2016 and 2018 describe these as possible causes, not a definitive diagnosis: 2016 discussion and 2018 discussion.
Try the safe checks first
- Disconnect unnecessary external storage. Shut the PC down and unplug USB drives, memory cards, and external disks that are not needed to start it. Leave essential peripherals connected, then turn the computer on again. If it still shows the error, continue to firmware checks.
- Check whether the internal drive is detected. Restart and enter BIOS/UEFI setup using the computer maker’s instructions; the key or procedure varies by model. Look for the SSD or hard disk in the firmware’s storage or device list. If it is absent, Windows repair commands cannot fix a device the firmware cannot see. The issue may involve the connection, power, firmware detection, or drive failure. Follow the manufacturer’s service guidance rather than opening a laptop or desktop without considering its instructions.
- Confirm the boot target. If the drive is listed, check the firmware boot order and select Windows Boot Manager or the drive that contains the Windows installation as the first boot target. On a PC with more than one internal drive, firmware may be trying the wrong one. Menu names and available entries vary, and UEFI/legacy settings are system-specific; do not change unrelated settings at random.
- Use Windows recovery tools if detection and boot order look right. When the drive appears and the correct target is selected but Windows still will not start, use Windows recovery options or installation media to access repair tools such as Startup Repair. Follow Microsoft’s current instructions for creating and using installation media: Create installation media for Windows. The older Microsoft community discussions mention installation media and boot configuration repair, but they are not a current, complete command-by-command repair guide. Avoid commands that alter partitions or boot data unless you understand the specific instructions for your system.
Choose the next step based on what you find
| What you find | What it suggests | Next step |
|---|---|---|
| Internal drive is not listed in BIOS/UEFI | Firmware is not detecting the device; a connection, power, firmware, or drive problem is possible. | Do not format or run Windows boot-repair commands. Check model-specific service guidance; if the drive may be failing and files matter, prioritize data protection. |
| Drive is listed, but a different device or entry is first | The PC may be trying to start from the wrong target. | Select Windows Boot Manager or the drive containing Windows as the first boot target. |
| Drive and intended boot target are listed, but startup still fails | Boot information or partition state may be damaged, among other possibilities. | Try Windows recovery tools and follow current official instructions. Protect important files before steps that write to the drive. |
| The issue began after a hardware or firmware change | The selected drive, boot entry, or boot mode may no longer match the Windows installation. | Recheck which drive contains Windows and which entry the firmware is using. There is no single BIOS reset recipe established for every PC. |
Protect files before attempting repairs
If the files are important, avoid formatting, a clean Windows installation, repeated write attempts, or partition-changing commands until you have a backup or a recovery plan. A drive that is failing may become less accessible, and the available evidence does not guarantee that any particular recovery method will work. If firmware cannot see the drive or there are signs of physical failure, consider qualified data-recovery help before further attempts to start or repair it.
If you need Windows installation media, use Microsoft’s instructions and suitable USB media you already have; the cited sources do not establish a required USB capacity. A prepared USB can provide access to recovery tools, but it cannot fix a drive that firmware does not detect.
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