First, check and correct the boot order in BIOS/UEFI to ensure the Windows drive is the primary boot device. 2. Verify the Windows drive is detected in BIOS under storage or drives. 3. If not detected, troubleshoot hardware connections by reseating SATA and power cables for desktops or reseating the M.2/SATA SSD in laptops, and test the drive on another system if possible. 4. If the drive is detected but won’t boot, repair the bootloader using a Windows installation USB by running bootrec /fixmbr, bootrec /fixboot, bootrec /scanos, bootrec /rebuildbcd, or bcdboot C:\Windows. 5. If issues persist, run chkdsk C: /f /r to check for disk errors or corruption, and consider reinstalling Windows if necessary after attempting data backup. The error is typically resolved by correcting boot order or repairing boot configuration, but drive failure may require replacement.

The "Reboot and Select Proper Boot Device" error on a Windows PC means your computer can't find a bootable operating system. This usually happens because the system can't detect the drive where Windows is installed. Here’s how to diagnose and fix it, step by step.

1. Check Boot Order in BIOS/UEFI

The most common cause is that the PC is trying to boot from a device that doesn’t have an OS (like a USB drive or CD). You need to ensure the correct drive (usually your SSD or HDD with Windows) is set as the primary boot device.

Steps:

• Restart your PC.
• As it starts up, press the BIOS/UEFI key (commonly F2, F10, F12, Delete, or Esc — varies by brand).
• Go to the Boot tab.
• Make sure your main hard drive or SSD (the one with Windows) is at the top of the boot order.
• If your drive doesn’t appear in the list, it may not be detected — skip to step 3.
• Save and exit (usually F10).

? Tip: If you recently plugged in a USB drive or external device, unplug it and reboot — it might be interfering.

2. Check if Windows Drive Is Detected

If the drive isn’t showing up in BIOS, Windows can’t boot from it.

What to do:

• In BIOS, look for a section like Storage, Drives, or Main.
• Check if your SSD/HDD appears in the list.
  • ? If it does appear, go to step 4 (likely a boot configuration issue).
  • ? If it doesn’t appear, continue to step 3.

3. Troubleshoot Hardware Connection

A missing drive often means a loose or failing connection.

For desktops:

• Power off and unplug the PC.
• Open the case.
• Check that the SATA and power cables to your drive are securely connected.
• Try switching to a different SATA port on the motherboard (and update BIOS boot settings accordingly).
• If you have another PC, test the drive there.

For laptops:

• This is trickier, but if you're comfortable, open the back panel and reseat the SSD (especially if it's an M.2 NVMe or SATA SSD).
• Look for signs of physical damage or overheating.

?? Note: If the drive still isn’t detected after reseating, it may be dead. Try replacing it or using a USB-to-SATA adapter to check if it shows up on another computer.

4. Repair the Bootloader (Windows Startup Repair)

If the drive is detected but the system still won’t boot, the bootloader or boot configuration data (BCD) may be corrupted.

You’ll need a Windows installation USB/DVD:

• Insert the USB and boot from it (select it in BIOS or press F12 during startup for boot menu).
• Choose your language, then click Repair your computer (bottom-left).
• Go to Troubleshoot > Advanced Options > Command Prompt.

Run these commands one by one:

bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd

? If /scanos or /rebuildbcd finds your Windows installation, this often fixes the issue.

Alternatively, try:

bcdboot C:\Windows

(Replace C: with the correct drive letter if Windows is on D: or another letter — check using dir C:\ or dir D:\Windows.)

5. Check for Drive Failure or Corrupted OS

If the drive is detected and the bootloader repair fails:

• Use the Command Prompt from the installation USB to check the disk:

  chkdsk C: /f /r

  (Again, adjust the drive letter as needed.)

• If chkdsk fails or the drive is unreadable, the OS may be corrupted or the drive failing.

? Consider reinstalling Windows as a last resort (after backing up data if possible).

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Summary Checklist:

• [ ] No external devices plugged in during boot
• [ ] Correct boot device selected in BIOS
• [ ] Hard drive/SSD detected in BIOS
• [ ] Cables reseated (desktop) or SSD reseated (laptop)
• [ ] Bootloader repaired using Windows installation media
• [ ] Drive tested on another system if needed

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If none of the above works, the drive may be dead — time to replace it and restore from backup. But in most cases, fixing the boot order or repairing the BCD resolves the issue.

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