You install Linux alongside Windows, reboot, and Windows has vanished from the menu, or there is no menu at all. Nothing is actually lost. A broken Windows boot after a Linux install is almost always a bootloader that simply does not know Windows exists yet, and pointing GRUB back at the Windows partition takes two commands.

Quick Answer

Boot into your Linux install, run os-prober so it scans every drive for other operating systems, then run "sudo update-grub" to rebuild the boot menu with Windows added back. Two commands restore the Windows entry in most cases. Your Windows files were never touched, only the boot menu changed.

Why this happens

When you install Linux for dual-boot, it installs GRUB, the Linux bootloader, and GRUB becomes the first thing that loads. If GRUB was generated without scanning for other systems, it lists only Linux, so Windows is present on the disk but invisible at boot. The fix is to make GRUB detect the Windows partition and add an entry for it. This is a configuration problem, not data loss, which is why it is usually quick to put right.

The fix, step by step

  1. Boot into your Linux installation normally. If GRUB shows only Linux entries, select Linux and log in.
  2. Open a terminal.
  3. Ensure os-prober is enabled. On recent distributions it can be disabled by default; if so, set GRUB_DISABLE_OS_PROBER=false in /etc/default/grub, then save.
  4. Run "sudo os-prober". It scans all drives and should report the Windows installation it finds. Seeing Windows listed here confirms the next step will work.
  5. Run "sudo update-grub". This rebuilds the boot menu and adds the detected Windows entry.
  6. Reboot. The GRUB menu should now list both Linux and Windows.

If os-prober finds Windows but it still does not appear, double-check that GRUB_DISABLE_OS_PROBER is set to false and run update-grub again.

If GRUB itself never loads

Sometimes the problem is the reverse: Windows boots straight away and Linux, or the menu, never appears, which usually means the firmware is booting the Windows bootloader directly. Enter your motherboard's UEFI boot menu (commonly Delete or F2 at startup) and check the boot order. Make sure the GRUB or Linux entry is set above the Windows Boot Manager. Some systems also need Secure Boot or Fast Boot adjusted before GRUB will take over. Once GRUB loads first, the os-prober and update-grub steps above add Windows back to its menu.

Avoiding it next time

The cleanest way to avoid this is to let the Linux installer detect Windows during installation, which means installing Linux after Windows rather than before. Keeping both systems on the same UEFI mode, rather than mixing UEFI and legacy BIOS, also prevents a lot of boot confusion. Healthy, fast storage helps the whole dual-boot experience too, and current drives sit in the PC best sellers if you are adding a second SSD to give each system its own partition. For portable Linux tinkering, compact systems like those in the handheld gaming console range often run the same GRUB-based setup, so the same fix applies there.

Frequently Asked Questions

Did installing Linux delete Windows?

Almost never. The most common cause is that GRUB was built without scanning for Windows, so the files are intact but the boot menu does not list them. Running os-prober and update-grub usually brings Windows straight back.

What does os-prober actually do?

It scans all connected drives for other operating systems and reports what it finds. update-grub then uses that information to add the detected systems, such as Windows, to the GRUB boot menu.

Why is os-prober disabled by default on some distributions?

Some distributions disable it for security and predictability reasons. For dual-boot you need it on, so set GRUB_DISABLE_OS_PROBER=false in /etc/default/grub, then re-run update-grub.

Windows still will not show after update-grub. What now?

Confirm os-prober actually detected Windows. If it did not, check that both systems use the same UEFI mode and that the Windows EFI partition is intact. Then verify the firmware boot order lists GRUB ahead of the Windows Boot Manager.

Can I fix this from Windows instead?

You can repair the Windows bootloader from Windows recovery, but that typically makes Windows boot first and hides Linux. For a working dual-boot menu, fixing GRUB from the Linux side with os-prober and update-grub is the cleaner route.

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