You need to boot in UEFI mode but do not want to convert your disk to GPT (with mbr2gpt for instance)?
-free some disk space (by shrinking you main partition for instance)
-create a FAT32 partition
-make your partition bootable with bcdboot c:\windows /s g: /f all (with g: being your new partition)
-now, shutdown your computer, modify your bios to UEFI, reboot and enjoy!