Problems dual-booting Win 7 & Win 10 - BCD seems wrong

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Problems dual-booting Win 7 & Win 10 - BCD seems wrong

Postby Ambertus » Sun Feb 26, 2017 10:25 pm

I originally had 32-bit Win 7 Pro installed on my laptop, but then I installed 32-bit Win 10 Pro; they're both on the same physical drive, but in two different NTFS partitions (they're both small, so they use MBR booting rather than UEFI). But Windows 7 usually doesn't boot (it often does if I use BIBM's Direct Boot, but that's the only way and it doesn't always work). Apparently the Win 10 boot manager (which I loathe) takes over from BIBM and -- for whatever reason -- Win 7 doesn't boot so it always boots Win 10 instead.

I believe that the fault lies in the Win 7 BCD. I have this Win 7 / Win 10 Pro with BIBM working perfectly on my desktop computers (three of them), but when I use BIBM to look at the BCDs, all 3 of the desktops have completely different entries than the laptop. Unlike the others, the only entry in Win 7's BCD is a "Resume" entry, with no main boot entry at all! I tried deleting it (using BIBM) then creating one that matches one of the desktop's exactly, which worked exactly ONCE before it was mysteriously replaced with another "resume" entry again (I'm lookin at you, Microsoft! :evil: )

On the other hand, my manually created entry may have been deleted because the GUID I copied from a desktop BCD might not have been correct for the laptop. Anyone know how I'm supposed to determine the correct GUIDs to use for a particular BCD entry?

Anyway, how do I fix this troubling problem? And ideally make the horrific Win 10 boot manager go away or at least remain invisible?

Thanks!
Ambertus
 
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Re: Problems dual-booting Win 7 & Win 10 - BCD seems wrong

Postby Ambertus » Mon Feb 27, 2017 5:24 pm

It seems that BIBM just might possibly be (at least one of) the culprits here, shocking though that sounds -- it's a truly excellent product, after all!

Here's why I think that possibility exists: I finally managed to fix the problem using BoyAns.net Visual BCD Editor (stay away from EasyBCD!). The problem turned out to be that something kept altering the target partition from volume # 2 (Windows 7 Pro) to volume # 4 (Windows 10 Pro and it's awful bootloader). It seems very likely that it was Windows 10 itself doing that, but I'm not sure.

Anyway, my changes bypassed BIBM (as expected, since the boot partition was set to volume 2, while BIBM resides on volume 1), so once I verified that the problem was fixed by booting both OS's successfully, I re-activated BIBM v1.35c. But when I rebooted and selected Win 7 from it's boot menu, all my problems were suddenly back again! It would NOT boot Win 7, and instead it immediately tried to boot Win 10! And again, the Win 10 boot loader failed to boot Win 7 (the computer restarted instead). And when I looked at the Win 7 BCD again with the Visual BCD Editor, sure enough I found that the Win 7 boot entry pointed to volume 4 again! :evil:

Now, I'm well aware that that's far from proof that BIBM is to blame, but there certainly seems to be something highly undesirable going on. It's probably still Win 10's fault, but since I can only get Win 7 & Win 10 to dual-boot by disabling BIBM and using the Win 7 boot loader, perhaps BIBM is somehow involved after all?

Whaddyathink?
Ambertus
 
Posts: 35
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Re: Problems dual-booting Win 7 & Win 10 - BCD seems wrong

Postby TeraByte Support(PP) » Mon Feb 27, 2017 7:05 pm

Are you using limited primary partitions? Normally, it's good to keep Windows isolated since issues can arise if they see each other.

How are the Windows 10 and Windows 7 boot items configured in BIBM? Which partition is set to boot? Which partition(s) in MBR? Any hidden partitions? What other options are set? Have you tried recreating either (or both) of the boot items?

If both Windows 10 and Windows 7 are booting from the same partition (and same BCD) then directly booting Windows 7 is more difficult. Booting each from their own partition is recommended (along with having each BCD configured only for the one Windows).

You can also edit BCD files in BIBM by using Partition Work, selecting the partition, and clicking the "BCD Edit" button.
Paul Purviance
TeraByte Support
TeraByte Support(PP)
 
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Re: Problems dual-booting Win 7 & Win 10 - BCD seems wrong

Postby mashedmitten » Wed Mar 01, 2017 4:44 am

The correct BCD entry will show which partition it's linked to. Bad ones will say no boot or have no partition listed on the edit page for it. The bogus entries get created when you don't re-auth BIBM directly after an OS install, letting Windows boot mgr. take over. You need to find the good entries, delete bad and redo Boot Edit entries to link to the correct paths.

You say you used entries from a desktop on a laptop? :?
mashedmitten
 
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