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I've been trying to boot up my Win7 USB stick into EFI mode as the disk I want to install it on, is GPT. I have tried to modify the installation media (including copy bootmgr.efi, bootx64.efi and such), but I keep getting a winload.efi file is missing error, which is a bit weird because setup disks aren't supposed to have a system32 folder containing a winload.efi file.

My Motherboard certainly supports EFI boot. When inserting my flash drive, I get two options for boot, one bios and one UEFI. Also, I've installed Win8.1 on a GPT disk, as well as a previous win7 install, which I seem to have forgotten how I managed to make it work.

I've tried going through a lot of topics, and the entire idea about EFI boot using files still remains very foggy in my head.

So I w would really appreciate it if I get a clear idea of how EFI boot works in this case(more from the perspective of what files are needed):

  1. What are the files needed for EFI boot for a windows setup USB?
  2. What files have been renamed but are actually similar files? (such as bootmfgw.efi and bootx64.efi)

And the purpose of the other folders/files(correct me if I'm wrong):

  • sources: files Windows needs during installation, including the .wim file.
  • boot: BIOS installation boot files
  • support: additional tools
  • autorun.inf, setup.exe: Files needed for Autorun

My motherboard also has an option to Launch EFI shell from file system device, requiring it to have a shellx64.efi file. Is this the same as the bootmgr.efi file? Will copying/renaming it work?

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prepare usb stick with rufus and point it to the windows iso, selecting gpt and fat32. rufus will prepare and populate the efi/ directory on the stick, so you can install windows 7 in efi mode.

Pingers

  • Can you go into a little more detail on what Rufus is and why it is a better technique than the one the OP is currently using? – Burgi Jan 14 '16 at 15:44
  • Ah I had no idea Rufus prepped the WinPE by itself. – RiA Jan 14 '16 at 19:55
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    rufus is just one of the many tools to prepare a usb stick for various operations. It's handy for a windows 7 usb, cos it saves having to prepare the efi folder manually. The standard iso does not have a complete efi folder. You can do it manually by simply making a fat 32 partition gpt and copying the windows files out of the iso and onto the stick but it won't boot in efi mode until you prep the efi/ folder manually – Pingers Jan 14 '16 at 20:26
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    EFI/ EFI/microsoft EFI/microsoft/boot EFI/microsoft/boot/fonts EFI/microsoft/boot/fonts/cht_boot.ttf EFI/microsoft/boot/fonts/jpn_boot.ttf EFI/microsoft/boot/fonts/chs_boot.ttf EFI/microsoft/boot/fonts/wgl4_boot.ttf EFI/microsoft/boot/fonts/kor_boot.ttf EFI/microsoft/boot/bcd EFI/microsoft/boot/efisys.bin EFI/microsoft/boot/cdboot.efi EFI/microsoft/boot/efisys_noprompt.bin EFI/microsoft/boot/cdboot_noprompt.efi EFI/boot EFI/boot/bootx64.efi – Pingers Jan 14 '16 at 20:28
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    the bootx64.efi is a renamed clone of c:\Windows\Boot\EFI\bootmgfw.efi which is available from any installed copy of windows – Pingers Jan 14 '16 at 20:34
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After a bit of tampering with additional ISOs, I've realized that you can just replace the \sources\install.wim file on a Win 8/8.1/10 bootdisk with the one from Win7 to make it work.

  1. Just get a Win8/8.1/10 ISO
  2. Open it using an ISO-explorer (like UltraISO)
  3. Replace \sources\install.wim with that from the Win7 ISO/DVD
  4. Save as a new ISO, and/or burn it into the installation DVD or on a USB/external HDD active Fat32 partition.

The installation UI will be of the bootdisk's Win version, but it will certainly install Windows7.

Conclusion: Perhaps, (my) Windows 7 efi boot files are just... broken.

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