


how to fix 'an operating system wasn't found' on win startup
Aug 01, 2025 am 05:29 AMRestart the computer and enter BIOS/UEFI by pressing the appropriate key (such as F2, F10, Del, or Esc) during startup. 2. Navigate to the Boot tab and ensure the primary hard drive or SSD containing Windows is set as the first boot device, then save and exit. 3. If the drive is not listed, it may be disconnected, failed, or undetected—check hardware connections or replace the drive if necessary. 4. If the drive is detected but the system still won’t boot, access the Windows Recovery Environment (WinRE) to repair the boot process using built-in recovery tools.
If you're seeing the error "An operating system wasn't found" when starting your Windows PC, it means the system can't locate or load the OS from the boot device. This doesn't always mean Windows is gone — it could be a boot configuration issue, drive detection problem, or corrupted system files. Here’s how to fix it step by step.

1. Check Boot Order in BIOS/UEFI
The most common cause is that your PC is trying to boot from the wrong device.
Steps:

- Restart your computer.
- Press the BIOS/UEFI key (usually
F2
,F10
,Del
, orEsc
— varies by manufacturer) during startup. - Go to the Boot tab.
- Make sure your primary hard drive or SSD (the one with Windows installed) is set as the first boot device.
- Save and exit.
? If your drive doesn’t appear in the boot list, it could be disconnected, failed, or not detected — proceed to step 3.
2. Use Windows Recovery Environment (WinRE)
If the OS drive is detected but won’t boot, repair the boot process using built-in tools.

How to access recovery:
- Use a Windows installation USB/DVD.
- Boot from it (change boot order if needed).
- Choose "Repair your computer" > Troubleshoot > Advanced Options.
Now try these fixes:
? Startup Repair
- Select Startup Repair.
- Let Windows automatically fix boot issues (e.g., missing or corrupt boot files).
? Repair Boot Configuration Data (BCD)
If Startup Repair fails, manually rebuild the BCD:
- Open Command Prompt from Advanced Options.
- Run these commands one by one:
bootrec /scanos bootrec /fixmbr bootrec /fixboot bootrec /rebuildbcd
- Restart after completion.
? If
rebuildbcd
finds Windows but won’t add it, make sure you're using the correct Windows installation (especially if multiple drives exist).
3. Check if Drive Is Detected
If the drive isn’t showing up in BIOS or recovery tools:
- Reseat the drive: Power off, unplug the SATA or NVMe drive, then reconnect it.
- Try a different SATA port or cable (for SATA drives).
- Test the drive on another PC if possible.
- Listen for unusual noises (clicking = possible hardware failure).
If the drive still isn’t detected, it may be dead or failing — consider data recovery options.
4. Verify Disk Mode in BIOS (AHCI vs RAID vs IDE)
Sometimes changing SATA mode breaks booting.
- Enter BIOS.
- Look for SATA Operation or Storage Mode.
- If it was AHCI and now is RAID, switch back (or vice versa).
- ?? Changing this after OS install can cause boot failure.
Note: If you must change it, you might need to boot with
Safe Mode
or reinstall Windows.
5. Reinstall Windows (Last Resort)
If all else fails and you can’t recover the OS:
- Back up data (if drive is readable via another PC).
- Use a Windows USB installer to clean install Windows.
- During setup, delete old partitions and let Windows create new ones automatically.
Final Notes
- UEFI vs Legacy BIOS: Ensure boot mode matches your disk’s partition style (UEFI → GPT, Legacy → MBR).
- Fast Startup/Safe Boot: Disable Secure Boot temporarily if it interferes (re-enable after fix).
- Always test with a known-good bootable USB to rule out media issues.
Fixing "An operating system wasn't found" usually comes down to boot order, corrupted boot records, or drive failure. Most cases can be resolved without reinstalling Windows — start with BIOS and recovery tools.
Basically, check what the system sees first, then repair how it tries to start.
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