Reboot and Select proper Boot device or Insert Boot Media is selected Boot device and press a key for windows 8.1

Dear Chouhan Tarndeep,

Thank you for reaching out to the Microsoft Q&A.

The message "Reboot and Select proper Boot device or Insert Boot Media in selected Boot device and press a key" means that your computer's BIOS/UEFI (the initial startup software) cannot find a bootable operating system (in your case, Windows 8.1) on any of the storage devices it's checking.

You could try following these steps below to check:

1. Check for External devices:
   • Remove all USB drives, memory cards, and external hard drives.
   • Eject any CDs or DVDs from the disc drive.
   • Restart your computer then try again.
2. Check the Boot Order in BIOS/UEFI:
   • Restart your computer.
   • As soon as it starts, repeatedly press the key to enter the BIOS/UEFI setup. Common keys are F2, F10, F12, or Delete (DEL). The correct key is usually displayed on the screen for a moment during startup (e.g., "Press F2 to enter Setup").
   • Once in the BIOS setup, use the arrow keys to navigate to the "Boot" or "Boot Order" tab.
   • You will see a list of devices. Make sure that your primary hard drive or SSD (the one with Windows 8.1 installed) is at the top of the list (first boot device). It might be listed by its model name (e.g., "SAMSUNG SSD 970 EVO") or as "Windows Boot Manager".
   • If it's not first, follow the on-screen instructions to move it to the top.
   • Navigate to the "Exit" tab and select "Exit Saving Changes" (this is often done by pressing the F10 key).
   • The computer will restart.
3. Check physical connections (For Desktop PCs):
   • Turn off and unplug your computer completely.
   • Open the computer case.
   • Locate your hard drive or SSD.
   • Check the two cables connected to it: the SATA data cable (a thin, flat cable) and the SATA power cable (a slightly wider cable from the power supply).
   • Unplug both cables from the drive and the motherboard (for the data cable) and plug them back in firmly to ensure they have a secure connection.
   • Close the case, plug the computer back in, and try to turn it on.
   Note: Only do this if you are comfortable opening your computer case.

If after all these steps the problem persists, it could unfortunately indicate a more serious issue, such as a failing hard drive. In this case, you need to find for manufacturer's support. They will be able to determine if a hardware replacement is necessary.

To assist others who might have similar questions and to help us improve our support system, we kindly encourage you to "Accept the answer" if it successfully addressed your concern. Accepting an answer lets other users know that this solution worked for you, and it also helps us track the effectiveness of our support efforts.

Best regards, 

Bryan Vu | Microsoft Q&A Support Specialist