Windows won’t start

Dual-boot menu missing or wrong OS loads automatically

On a PC set up to boot into two operating systems (such as Windows and Linux), the selection menu no longer appears, or the PC always loads the same OS without giving you a choice.

Difficulty
Advanced
Time
30–90 minutes
DIY cost
$0
Pro cost
$80–$200

Symptoms

  • Boot menu that used to appear no longer shows
  • PC always loads the same OS regardless of preference
  • Started after installing or updating one of the operating systems
  • The other OS still exists on the drive but isn't reachable at boot

Likely causes

  • CommonWindows Update overwrote the boot loaderWindows updates sometimes reclaim control of the boot process, hiding other OS entries.
  • CommonFast Startup or Secure Boot settings blocking the other OSThese features can prevent a non-Windows boot loader from running.
  • PossibleBoot menu timeout set to zero or very shortA misconfigured timeout can skip the menu before you can react.
  • PossibleBoot order changed in BIOS/UEFIThe BIOS may now be pointing directly at one OS's boot entry, bypassing the shared menu.
  • Less commonBoot loader on the other OS's partition damagedAn update or disk change may have corrupted the second boot loader.

What to do

  1. Check BIOS/UEFI boot order first; if entries for both operating systems exist, try selecting the other OS's boot entry directly to confirm it still works.
  2. Disable Windows Fast Startup (Control Panel > Power Options > Choose what the power buttons do) since it commonly interferes with dual-boot menus.
  3. If you dual-boot with Linux, boot into a Linux live USB and use 'sudo update-grub' or reinstall GRUB to the correct drive to restore its menu.
  4. If Windows Update removed the boot menu, the other OS's boot loader may need to be reinstalled from its own recovery/live media following that OS's instructions.
  5. Check that Secure Boot settings in BIOS/UEFI are compatible with the non-Windows OS if that's part of the setup; adjust as that OS's documentation recommends.
  6. Increase the boot menu timeout if it's set very short, either through 'bcdedit /timeout' in Windows or the other OS's boot loader configuration.
  7. If you're not comfortable with boot loader repair, back up important data on both OS partitions before further troubleshooting since these repairs touch the disk's partition boundaries.

Tools and parts

  • Linux live USB or the second OS's recovery media, if applicable

When to call a pro

Restoring a dual-boot menu after Windows Update overwrites it can be tricky; a technician experienced with multi-boot setups can save time if your own attempts don't restore the menu.

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.