I noticed that in Windows 7 Ultimate 64-bit image there exist bootmgr.efi and winload.efi and I applied it to my computer. Then I edited my BCD to add an option to boot it. When attempting to boit in UEFI mode, Windows 7 always gets stuck at disk.sys and shuts down automatically. However there's nothing wrong when booting in legacy mode (boot winload.exe instead of efi). How exactly can I boot that Windows 7 in UEFI?
My computer originally had Windows 8.1 installed on it out-of-the-box and I turned boot mode to "UEFI with CSM" in BIOS settings.

Edit: Problem solved. My solution is to first boot into Win7 under LEGACY mode, install chipset driver (pre-downloaded from Intel) and then switch back to UEFI-CSM. Now Windows 7 no longer crashes at disk.sys.
But can anyone explain why it's related to chipset driver???

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    Are you booting from Windows 7 64 DVD/USB or you already have Windows 7 64 installed on your system and now it's not booting? Are you aware what type of Disk Partitioning scheme exists for your hard drive, is it MBR or GPT? Windows 7 shall boot in UEFI mode with GPT partition scheme Hard drive. – patkim Feb 19 '17 at 2:22
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    It's GPT and the boot partition is an EFI System Partition. The BCD was originally created by Windows 10 (stock 8.1 got formatted). I only applied the Windows 7 image to another partition on my hard drive and added an entry for it with Bootice. I have a secondary drive that's MBR so I am able to create an alternative boot record using bcdboot.exe and then comes the question. – iBug Feb 19 '17 at 12:17
  • Could you link this chipset driver? – mirh Feb 19 '17 at 16:04

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