What I have:

  • Windows 10 booting from GPT drive via UEFI.
  • A partitioned MBR drive with two Windows 7 installations.
  • Machine can boot into Windows 10, but not the Windows 7 installations.


What I'd like:

  • A boot menu containing all three OSes.


Available tools:

  • Win 7 and Windows 10 64 bit installation media, on both DVD and USB.
  • AOMEI Partition Assistant Pro which can convert a disk from MBR to GPT and visa versa without losing data.


Complications/details:

I tried using EasyBCD, which claims to support Windows 10 and UEFI, but it broke my BCD such that I couldn't boot into any OS. Took me a full day of research, trial and error to get it booting in Windows 10 again. In the process, I may have screwed up the boot records for the Windows 7 installations.


My BIOS (new Asus motherboard) used to show all my installations, and it would let me boot directly into each of them via "Boot Override" function. Now it only shows the Windows 10 installation.


If I run `bootrec /ScanOs` it shows all the Windows installations. I've run `bootrec /RebuildBcd` and said "yes" to each OS, but the machine still boots directly into Windows 10.


I tried running recovery tools on the Windows 7 installation disk, and it tells me I can't because I have the wrong version of Windows (it's the same disk I used to install Windows 7, but it sees Windows 10 and refuses to let me continue).


I used bcdedit to add one of my Windows 7 partitions to the Windows Boot Manager:


Code:
Windows Boot Manager -------------------- identifier {bootmgr} device partition=\Device\HarddiskVolume2 path \EFI\MICROSOFT\BOOT\BOOTMGFW.EFI description Windows Boot Manager locale en-us inherit {globalsettings} default {current} resumeobject {3efead84-5517-11e5-a453-d7730d7389bf} displayorder {current} {3efead86-5517-11e5-a453-d7730d7389bf} toolsdisplayorder {memdiag} timeout 5 Windows Boot Loader ------------------- identifier {current} device partition=C: path \Windows\system32\winload.efi description Windows 10 locale en-us inherit {bootloadersettings} isolatedcontext Yes allowedinmemorysettings 0x15000075 osdevice partition=C: systemroot \Windows resumeobject {3efead84-5517-11e5-a453-d7730d7389bf} nx OptIn bootmenupolicy Standard Windows Boot Loader ------------------- identifier {3efead86-5517-11e5-a453-d7730d7389bf} device partition=E: path \Windows\system32\winload.efi description Windows 7 DAW locale en-us inherit {bootloadersettings} isolatedcontext Yes allowedinmemorysettings 0x15000075 osdevice partition=E: systemroot \Windows resumeobject {3efead84-5517-11e5-a453-d7730d7389bf} nx OptIn bootmenupolicy Standard
This adds "Windows 7 DAW" to the Windows Boot Manager. When the disk containing Windows 7 was MBR, selecting that option just crashes the machine and causes a reboot. If I change that disk to GPT, it bluescreens saying \Windows\system32\winload.efi (or \Windows\system32\winload.exe; I tried both) is corrupt.