Windows won’t start

'Reboot and Select proper Boot device' error message

The screen shows 'Reboot and Select proper Boot device or Insert Boot Media in selected Boot device' instead of starting Windows. This is a BIOS-level message meaning it can't find a valid drive to start from.

Difficulty
Intermediate
Time
20–60 minutes
DIY cost
$0–$60
Pro cost
$100–$220

Symptoms

  • Text-only error message on black screen mentioning boot device
  • Appears right after the BIOS/manufacturer splash screen
  • No Windows logo appears
  • May follow adding a new drive, BIOS update, or moving the PC

Likely causes

  • CommonBoot drive not detected or disconnectedA loose cable is the single most common cause of this specific message.
  • CommonIncorrect boot order in BIOS after a changeAdding a new drive can shift the boot order away from the Windows drive.
  • PossibleBoot partition corrupted or missing boot flagThe drive may be physically fine but missing the marker that tells BIOS it's bootable.
  • PossibleDrive failureA dead or dying drive won't present as bootable even if partially detected.
  • Less commonUSB device or card reader interferingAn empty card reader or unusual USB device can sometimes be mistaken for a boot target.

What to do

  1. Remove any USB drives, SD cards, or discs and restart the PC.
  2. Enter BIOS/UEFI setup and check the boot order list; move your main Windows drive to the top if it's listed but out of order.
  3. If the drive isn't listed in the boot order at all, check the storage/SATA info screen in BIOS to see if it's detected as hardware.
  4. For desktops, power off, unplug, and reseat the drive's SATA data and power cables.
  5. If detected but still not bootable, use a Windows installation USB, choose Repair your computer, and run 'bootrec /fixmbr', 'bootrec /fixboot', and 'bootrec /rebuildbcd' from Command Prompt.
  6. If the drive isn't detected by BIOS at all even after reseating cables, treat it as a likely hardware failure.
  7. Back up accessible data before further repair attempts if the drive shows any signs of intermittent detection.

Tools and parts

  • Bootable Windows installation USB drive
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When to call a pro

If the drive isn't detected in BIOS even after reseating connections, have a professional test the drive and cables, especially before attempting a reinstall that could complicate data recovery.

Safety

Generally low risk

Generally low risk for a careful person. Stop if anything looks different from what this guide describes.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.