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.

  • You can't 'fix' a BootCamp partition using Windows. It simply doesn't understand the format. Best options would be [or would have been, I'm not sure ether can rescue it now] WinClone or Paragon Hard Disk Manager - both of which can resize BC partitions non-destructively. See apple.stackexchange.com/search?q=bootcamp+resize for a swathe of similar issues. – Tetsujin May 4 '17 at 19:50
  • I did make a backup with Carbon Copy Cloner. Is there a way to boot to a usb flash drive of windows 8.1? – 1337GameDev May 5 '17 at 1:55
  • CCC can only restore to a ready-made & fully functioning partition. I'm also pretty sure that you cannot boot any Windows from USB other than specifically made WinToGo or Win10 structures. I'd be very tempted to see if Paragon can fix it. I've used it & it works well, but I've never had your particular situation to test it on. iirc, it has a fully-functioning 30-day demo. Alternatively, edit the results of these 2 terminal commands into your question diskutil list & diskutil cs list which may allow someone smarter than me to show you how to rebuild it manually. – Tetsujin May 5 '17 at 6:30
  • From other research, im pretty sure the only way to boot to windows usb flash volumes is with another bootloader (such as rEFIt or the like). CCC should work a slong as you make the partition the same size or larger than the prior bootcamp partition. So I would realistically use bootcamp to make that, and just restore using ccc. – 1337GameDev May 5 '17 at 15:41

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