Win7 x64 cannot be installed on an MBR disk under UEFI, but can be boot.
The scenario assumes that we have the CSM option enabled in the bios.
Installing the system in legacy mode (CSM on):
Win7 in legacy makes a 100MB Reserved partition by default but NTFS so go to CMD (Shift+F10) and manually partition:
diskpart
sel disk 0
clean
create par pri size=100
active
format fs=fat32
create par pri
exit
- continue the installation after closing the CMD window
- boot OS in legacy mode then:
- install GPU driver
- turn on showing hidden files in folder options
- add letter U: FAT32 partition 100MB in diskmgmt.msc
- make folder EFI\Boot - use 7-zip copy here file bootmgfw.efi from ISO\sources\boot.wim\1\Windows\Boot\EFI and rename to bootx64.efi
- copy Fonts folder from ISO\sources\boot.wim\1\Windows\Boot to EFI\Microsoft\Boot
- use BootICE export current BCD file to EFI\Microsoft\Boot
- use BootICE open exported BCD file and change ApplicationPath from winload.exe to winload.efi in Windows 7 section
Now you can reboot the system and boot into UEFI mode. You can also still boot in legacy mode
The same should be done with Win8/8.1/10