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Windows – common problems and fixes

Windows says "Operating System Not Found"

Topic #101 · Updated · Pataisoma.lt

Troubleshooting guide

How to fix the problem

BIOS check that the system disk is visible and the Boot priority is correct. If the drive is missing or making noises, stop the tests and take care of the data.

Possible solutions

Choose the method that matches your situation. Start with the simplest suitable option and check the result. If the problem is fixed, you do not need to continue with the other methods.

  1. Boot selection

    Disconnect the external media and BIOS select the correct system drive or Windows Boot Manager.

    Steps to follow

    1. Disconnect unnecessary external media and check the boot menu or BIOS key in the model manual.
    2. If you see UEFI Shell, type exit and Enter. If necessary, reboot and open the Boot/BIOS menu specified in the manual.
    3. See if the system SSD and Windows Boot Manager are listed; if available, select it. Do not change other modes.
    4. If the disk is missing or disappears, write the model and stop for data diagnostics. If the disk is present but the entry is missing, use Startup Repair.

  2. Startup repair

    If the drive is detected, use Startup Repair in the Windows recovery environment if you have a copy.

    Steps to follow

    1. Have a copy of important files and BitLocker key. If the drive disappears or makes noises, do not start this repair.
    2. In the available login window, Shift+Restart will open recovery; otherwise, choose "Repair your computer" instead of install from the prepared Windows USB.
    3. Open Troubleshoot > Advanced options > Startup Repair and select the system you need.
    4. Wait for completion and test the launch. If the repair fails, write a message; do not delete partitions.

  3. Undetectable disk diagnostics

    If the drive is missing or making unusual noises, stop the tests and try to save the data.

    Steps to follow

    1. Save important files if your computer or drive is stable. If it makes unusual noises, smells like burning or the battery is swollen, stop testing.
    2. Write down the exact pattern of when the problem started and what action it took to reoccur. Take a picture of the visible error or deformation without opening the case.
    3. Submit a repair request with this information.

If the problem persists

Disconnect the external drives and leave the correct internal boot device. If it is detected, use Startup Repair; if not detected, reinstalling Windows will not fix the hardware problem.

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