This question already has an answer here:

I installed Ubuntu 16.04. I already had windows 8 installed. Ubuntu 16.04 has been installed in legacy mode and windows 8 has also been installed in legacy mode(not sure about windows 8). After dual booting Ubuntu I cant boot to windows 8. The grub menu does not show windows 8 boot option i.e windows boot manager. I also tried boot repair disk but nothing happened. Secure boot is off.I even disabled legacy support in boot options but then the grub menu does not show up and windows 8 still does not boot. The summary of boot info is given in the following URL: http://paste.ubuntu.com/23979164/ Please help.

marked as duplicate by karel, Fabby, waltinator, anonymous2, George Udosen Apr 19 '18 at 14:14

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • 1
    Please ignore the comments above. From Ubuntu please run, in terminal, sudo update-grub. If it doesn't find Windows please edit and update your question with that information. – user589808 Feb 12 '17 at 5:34
  • 1
    @CelticWarrior I ran the above command and it found windows 8 loader on /dev/sda1 – Mehran Jeelani Feb 12 '17 at 5:41
  • 1
    OK, good. Does it work now? – user589808 Feb 12 '17 at 5:42
  • @CelticWarrior Yes, a big thanks to you. I am very grateful to you. I was surfing the net for about 3 hours without any lead and now you provided me a solution. Again a big thanks. – Mehran Jeelani Feb 12 '17 at 6:07
  • You're welcome. I'll post it as an answer then. Please accept it when available. – user589808 Feb 12 '17 at 6:09

The already installed OS, Windows 8, for some unknown reason wasn't detected when you installed Ubuntu.

Considering Grub is already installed and works (Ubuntu boots), running the Grub updater should now find the other OS. In terminal:

sudo update-grub 

Grub should find Windows 8 now and add it to the boot menu. Reboot and try booting Windows.

Not the answer you're looking for? Browse other questions tagged or ask your own question.