Windows 7 installation from bootable USB

[tabbbs]

I know there are plenty of people here with a similar question, but I feel like my issue is specific enough to warrant its own thread.

I finished building my first setup yesterday. The final thing I need is an operating system. I put Windows 7 Professional x64 on a bootable USB and ran it from the motherboard's boot menu. I run into no errors except that my hard drive uses a "GPT partition". After doing some research, it seems that either the USB or motherboard is running WIndows in a BIOS mode which isn't compatible with GPT partitions. So I do some more looking around to see how I could resolve it. I also put an Ultimate Boot CD on a second USB. I now have these options:

- Reformat the HDD to use a BIOS-compatible partition, which I already know how to do, but in turn will give less functionality
- Figure out how to make the USB boot with UEFI compatibility

I tried removing the non-efi "bootmgr" from the USB, but now I just get a missing bootmgr error when I boot the USB.
I've also heard it will always boot into UEFI mode if it says "UEFI" before the USB label in the boot menu. It does have that on my Ultimate Boot CD, but not on my Windows USB. None of the options i've tried in the boot menu have done anything.

 

[tabbbs]

Looks like you are booting from USB thumbdrive in non-UEFI mode. Hence Windows expects HDD with MBR layout. If you want to install to HDD with GPT layout, then you need to boot installation USB thumbdrive in UEFI mode.

Probably Secure Boot is preventing Windows 7 from loading in UEFI mode (because Windows 7 UEFI loader is not signed for Secure Boot, unlike Windows 8/8.1/10 UEFI loader). For example, on ASUS motherboards you need to choose "OS type: Other OS" in Advanced Mode Menu->Boot->Secure Boot:

I installed Windows 7 bootable onto my USB once again. I do have an ASUS motherboard, so I selected "Other OS" in secure boot menu. Unfortunately, this doesn't seem to help. I still can't use the HDD. Should the "secure boot state" still be enabled when I choose "Other OS'? Is it supposed to disable secure boot?

 

[tabbbs]

Yes, Secure Boot is disabled when you selected "Other OS".

How did you prepare Windows 7 installation USB thumbdrive? It needs to have GPT layout, single FAT32 partition and \EFI\BOOT\BOOTX64.EFI file.

I found an identical problem in another thread and used a proposed solution.
I used Rufus tomake a bootable USB instead of Windows USB/DVDDownload Tool. I was able to set it to GPT for UEFI mode and make it a FAT32 partition. Apparently the Windows USB tool doesn't optimize it for both BIOS and UEFI, so I have to do it manually.

Thanks for the help!