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#360
A legacy bios system that boots from an MBR disk will boot from both FAT32 and NTFS. Most (if not all) UEFI systems that boot from a GPT disk require the EFI System partition containing the boot files to be FAT32. In the Windows installation structure the whole thing is considered the EFI System partition, so the whole thing needs to be FAT32. The mode you boot the USB flash drive in determines the mode that Windows will install in. Boot the flash drive with the UEFI firmware in UEFI mode and Windows will format the hard drive as GPT, create a FAT32 EFI System partition and set it up for UEFI booting. If the computer is in legacy bios mode - also called CSM in some UEFI firmware (or only has a legacy bios), then Windows setup will format the hard drive as MBR and create a System Reserved partition to hold the boot files and set it up for legacy booting.