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I've looked at other answers regarding this issue but none of them had the same configuration I have so this is new although related to other posts.

I had a dual boot Windows 7 and Ubuntu. What was a bit different than typical is that I had 2 physically separate HDs. The first one had GRUB and Ubuntu, the second one had Windows 7 only. The advantage I had with this setup is that I could physically remove the Ubuntu hard drive and then Windows 7 would boot up normally none the wiser that it used to be booted from GRUB.

After doing a Windows 10 upgrade, things changed. GRUB with Ubuntu hard drive in place still works but if I pull out Ubuntu hard drive, now Windows 10 boot fails with the message GRUB recovery command prompt.

So somehow the Windows 10 upgrade did something to the boot record of the Windows hard drive. I had thought that when I installed GRUB on the Ubuntu hard drive that it only affected Ubuntu hard drive and not the Windows 7 boot disk. Maybe that wasn't true and what was there got corrupted by Windows 10 upgrade.

So now the Windows hard drive has some aspects of GRUB on it that are now corrupted.

Suggestions on how to fix the Windows 10 boot?

user3799318
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  • Did you at some point install grub to a different drive? With both drives connect? Post this, just need one line. #To see what drive grub2 uses see this line - grub-pc/install_devices: sudo debconf-show grub-pc # for BIOS with grub-pc And as suggested in answer run Boot-Repair. If not fixed post link to the summary report it creates. – oldfred Dec 15 '16 at 00:19
  • Initially it was a w7 system only. Then I added another separate hd and loaded linux on it and grub so I could choose either linux or W7. I edited the default boot to be W7 perhaps that is when something modified the w7 hd boot record. to answer your question no, I didn't install grub to a different drive unless that happened when I changed the default boot from linux to w7. – user3799318 Dec 15 '16 at 13:55
  • Did you run the Boot-Repair summary report, post the link it gives. Otherwise we just are speculating on your configuration. – oldfred Dec 15 '16 at 16:03
  • I appologize for linux stupidity, but I don't quite understand this line – user3799318 Dec 16 '16 at 13:46

1 Answers1

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Windows 10 corrupted GRUB. Your best solution is to use Ubuntu installation media to reinstall GRUB (best bet is to run boot-repair).

  • In a configuration with 2 separate hd's when grub is installed does it make changes to both the linux hd and the windows hd? – user3799318 Dec 15 '16 at 13:51
  • no, it should only change the Ubuntu HD –  Dec 15 '16 at 14:07
  • That's what I thought. So somehow when the w10 upgrade happened it must have grabbed something from the ubuntu HD and put it on the W10 disk boot record since now with the Ubuntu disk disconnected I get this grub failure. I need to run that grub summary report. – user3799318 Dec 16 '16 at 00:28