I currently have windows8.1 installed using bootcamp prior, and want to expand it's partition size. The iMac has El Capitan installed.
I don't want to delete it, as I fear apple has locked me to windows10 for new bootcamp installs. I currently have shrunk my macOS partition, and formatted that as a FAT partition.
Then, windows wouldn't boot (which is expected as it's partition is now the wrong boot disk number).
To fix this, I can boot to a repair disc and run a few command line commands. The issue:
I prepared a win8.1 bootable flash drive, using mac terminal, as well as rufus / windows usb tool on another windows machine.
When I try to boot to it on the iMac, and hold down OPTION, it doesn't show up in the boot menu.
Why is this? How can I boot to this to repair my windows install?
The appropriate EFI files are present on the flash drive. I've also tried different flash drives, and redoing the process.