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I converted my EVO840 SSD containing windows 7 64-bit to GPT using gptgen, then I restarted and it say bootmgr is missing. So I went into CSM settings and switched boot control to UEFI only, then I can't see the disk in boot option anymore. I've also tried disabling secure boot, but to no avail. I've read that windows 7 64bit can boot from GPT disk with UEFI so what am I missing here?

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  • Secure Boot is an optional component of UEFI.
    – Ramhound
    May 6, 2017 at 2:11

1 Answer 1

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You should check that on disk there are:

  1. EFI System partition (about 100 MB or more)

  2. MS Reserved partition (128 MB - depends on disk size)

Then use bcdboot.exe utility:

bcdboot F:\windows /s Z:

F: is where Windows is, Z: is EFI System - change letters to reflect your mappings.

bcdboot.exe writes boot related files to EFI System(ESP).

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  • So I tried to create only the EFI System partition, ran ”bcdboot windowspartition:\windows /s systempartition:” no problem, either from recovery environment or windows partition. Then I tried to create the MSR partition too, but then the bcdboot command's flag /s gives "failed to create new system store", either omit the /s flag (if use windows 7 bcdboot) or use windows 8 bcdboot then the error will be gone. But no matter what, I had to either disable secure boot or change OS type in secure boot to "Other OS" to boot from the SSD successfully. I'm using windows 7 ultimate 64bit, what's wrong?
    – yuushin
    May 6, 2017 at 16:46
  • Windows 7 does not officially support Secure Boot. (Some versions did boot with it active, in my experience, but this seems to be sporadic.) Thus, having to disable Secure Boot is normal for Windows 7. If the system is booting OK at this point, I'd say your problem is solved. If not, please elaborate.
    – Rod Smith
    May 7, 2017 at 14:11

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