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My main system (Windows 7 UEFI) is on a SSD. I have a 2nd GPT hard drive I use for backup that is not plugged to the computer.

After unplugging the SATA cable of the SSD, I installed Windows 10 UEFI on the 2nd HD so if my SSD fails, I still have a functioning system I can use in the mean time.

The install went fine. But now when I unplug the HD and plug the SSD, Windows 7 won't boot. I think the Windows 10 install messed with the Windows Boot Manager in the BIOS and it prevents me from booting.

I have an image backup of the W7 boot partitions so I think I can restore everything back to normal... except that when I'll do that, Windows 10 won't boot.

So the question is: how can have on the same machine (i7 2600K, Asus P8P67 B2) 2 UEFI Windows (7 + 10) on 2 different drives that are not plugged at the same time?

Kimberley Furson
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  • It is certainly possible when you install each system with the other drive disconnected, though you will need to switch the boot disc when you switch boots. You should be able to repair the drives individually with each connected one at a time in order to make them separately bootable. – AFH Jan 31 '18 at 17:01
  • Windows 7 (SSD) and Windows 10 (HD) were installed separately (with the other drive unplugged). When you say "switching the boot disk", do you mean switching the SATA cable? Also, how can I repair the drives individually? Thanks for the pointers. – Kimberley Furson Jan 31 '18 at 17:10
  • No, I meant changing the hard disc boot priority in the boot settings. You shouldn't need to make hardware changes. I have a system with independent boot sectors on three different drives, and I have not managed to make either of them cross-boot from another drive, so I need to switch disc boot priorities. – AFH Jan 31 '18 at 17:20
  • Ok I understand now. I actually tried that but when I force the BIOS/UEFI to boot on my SSD (Win7), it tries for a sec, then goes back to the UEFI/BIOS. It may be because it tries to boot in "MBR mode" (don't know what it's really called, I mean not UEFI)? – Kimberley Furson Jan 31 '18 at 17:32
  • That's probably called Legacy Mode in the UEFI/BIOS boot settings: you will need to switch this, as well as the boot priority. – AFH Jan 31 '18 at 17:41
  • I may have a problem here because I can't switch from UEFI to Legacy mode in my BIOS/UEFI. I have as Asus P8P67 B2 motherboard and there's no such option. There's a firmware update for the B3 I tried to apply to my B2 but it didn't work. – Kimberley Furson Jan 31 '18 at 17:46
  • Is your Win7 SSD configured as MBR? This answer states: "Windows 7 on UEFI requires that the disk partitions use GUID partition table (GPT) rather than the traditional MBR partitioning format found on BIOS systems." So you may need to convert your Win7 disc from MBR to GPT. – AFH Jan 31 '18 at 18:01
  • The SSD is GPT. I'm really scratching my head here. I fear this may be an issue with my BIOS/UEFI firmware – Kimberley Furson Jan 31 '18 at 18:12
  • I've reached the head-scratching phase, too. I can't think of other suggestions at present. The independent boot records on my triple-boot system comprise two MBR/Legacy discs and one GPT/UEFI and they all boot on my MSI UEFI/BIOS. – AFH Jan 31 '18 at 19:04
  • I don't know if this is normal behavior or not but I can only boot when I select Windows Boot Manager. When I select my HD with Windows 10 directly to bypass the boot order, I get an error message "select proper boot device" – Kimberley Furson Jan 31 '18 at 19:31
  • This laptop I'm using is dual-boot. I normally boot Ubuntu with Grub and although there is a Windows Boot Manager entry in the boot list, that doesn't work: I need to go to System Setup (another Grub entry), which takes me to the UEFI/BIOS boot manager, where I select Windows Boot Manager. If WBM allows you to boot what you want, you may need to live with this, as I've learned to do. – AFH Jan 31 '18 at 19:42
  • Sure thing but it looks like the WBM is now configured for Win10 so when I plug my SSD back, it's still default to the WBM in the UEFI/BIOS but Win7 can't boot. I don't know if it's really clear, it can sound confusing! – Kimberley Furson Jan 31 '18 at 19:46
  • I think I understand your problem, but I don't think I could take it any further without hands-on on your machine. Sorry, I'm afraid I have run out of other ideas. I know there are clever things to be done with bcdedit, but that's outside my experience. – AFH Jan 31 '18 at 19:53
  • Thanks for your answers, at least I know what I want to do is feasible (maybe not with my motherboard though). Do you know by any chance a forum where I could find some answers? – Kimberley Furson Jan 31 '18 at 22:03
  • Sorry, but this is the best forum I know. Maybe someone else will pick it up in a day or two. If you get an answer, post back on this thread: I'd like to know. For what it's worth, I spent 7 hours today upgrading a W10/1703 system to 1709, after an endless succession of 4GB down-loads, followed by several boots, followed by install messages (in a couple of cases saying it had got to 100%), followed by restoration of the previous 1703 system, with absolutely no indication of why, at the time or on any logs I could find. Hence my use of Ubuntu for everyday work: Windows is not my favourite OS. – AFH Jan 31 '18 at 22:35
  • What actually happened, was that I had only one Windows Boot Manager instead of 2 (1 for each Windows). The thing is I don't know how my Win7 Boot Manager disappeared in the first place since I disconnected the drive when installing Win10... Running Bootrec /FixMbr Bootrec /FixBoot Bootrec /RebuildBcd with the Windows Repair cmd on the Win7 DVD install fixed it and added a second WBM. – Kimberley Furson Feb 01 '18 at 20:24
  • So are you saying that you have now found a solution? – AFH Feb 01 '18 at 21:51
  • Everything is now working so I guess I have!;) – Kimberley Furson Feb 01 '18 at 22:42
  • Great. I'd try and summarise the conversation, but I'm not sure what the critical elements are. Maybe you should answer yourself, since you know the relevant details. – AFH Feb 01 '18 at 23:44

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