Windows 10 will not allow Windows 7 EFI OS Loader

I have been testing this to see what might be going on. If you install Windows 7 in the UEFI configuration, which means Secure Boot is not enabled. Then you install Windows 10 using UEFI in Dual Boot mode, you end up with a Boot GUI with selections for Windows 10 and Windows 7.

If you select Windows 7, you will get the screen below, so you have lost the boot capability to Windows 7. Since Secure Boot is not enabled, I have to assume the Windows 10 boot manager will not recognize the Windows 7 EFI OS loader.

There are probably not a lot of folks running Windows 7 as UEFI, but something to keep in mind with the release of Windows 10. I have not tried installing Windows 7 after Windows 10 so not sure what it might do, assuming you could even boot the Windows 7 install media in UEFI mode.

I am not dual booting.

Gary said:

I am not dual booting.

And we need to know this? Why?

Clark,

What Win10 bld did you install. I had a similar error with a previous bld (can't recall which one caused the issue). My System partition was trashed (System Reserved) and has to be rebuilt. I managed to clean it up enough to boot (repair using the lower version OS)

There was also some discussion on the partition sizes being incompatible (100 MB vs. 350 MB) plus the extra partitions for EFI.

This is a serious flaw and MS knows there are issues. Maybe you came across one they missed - feed them.

Bill
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forgot to search for the error code 0xC0000428, but here ya go:

Solved Solution to 0xc000428 when dual booting Win7 and Win8

Status 0xc0000428 Windows cannot verify the digital signature of - Microsoft Community

also forgot to mention that I ran EasyBCD

Thanks for the replies. I have been doing more testing and realized this also happens in Windows 8.1. Because I run a parallel install (independent installs) I do not use the Boot GUI, so I did not see this until I noticed the problem in a forum.

In my case, there is an option under the Secure Boot section in the Bios which states what type of OS you can use, Windows UEFI or Other OS. It appears Microsoft has told the Secure Boot OSes to treat a Windows 7 UEFI loader as Other OS.

So, even though Secure Boot is off because the CSM is enabled, Microsoft feels a need to restrict the Windows 7 loader. Not sure why exactly since I can run Windows 7 in other modes fine without modifying the setting. The only reason I can think of is that the Secure Boot OS boot manager, which is responsible for starting Windows 7 in this situation, needs to unload certain checks it may do during the subsequent reboot if another Secure Boot OS was being started.

I think I have noticed this same type of error is presented when a Technical Preview build expires, but I haven't had that experience.

Maybe one day Microsoft will come out with a reasonable explanation but thanks to all who replied