Wipe mac os partition, but save bootcamp?

I have a mac mini with 2 drives in it. One has just macOS period. I don't want to touch that one. The other has another mac OS and a partition with bootcamp running windows8.1. I need to convert the macOS partition on the second disk to an NTFS partition for windows data. But it sounds like when I lose the macOS partition, I will also lose the ability to boot the windows partition. I did create the bootcamp partition from the macOS on the second drive--I'm realizing it might have been easier if I'd created it from the other drive.....

From what I understand, I could wipe the second drive, reinstall bootcamp to it, and still not be able to create a new partition on the disk, without fixing the partition table afterwards.....

So if I'm going to have to fix the partition table anyway, maybe I can just wipe the macOS partition from within windows, and then go back and fix the mbr? It's not a huge amount of work to reinstall my windows apps, but I'd rather not do it, espcecially if it's not even necessary. But maybe there are other issues?

So my questions are: is this likely to be possible to do this, and if so, what is the process for fixing the mbr. I don't mind using the command line, but I'm not an expert. I've done some mbr fixing in the past, but it's been a while.

Thanks in advance for any tips!
-eric

 

Go to all EFI?

Okay, reading around here some more, and came up with a theory. Can anybody suggest if it is feasable, or how it could be modified to work? If it did work, it seems like I would also benefit from faster boot times.

1. Ignore warnings and wipe macOS partition from second disk
2. Format free space as NTFS from within windows
3. Use GPT fdisk to convert the MBR to EFI. Shut down.
2. Boot with option key, select macOS on the first disk. Should still be possible?
3. Install rEFInd to the macOS.
4. Boot via rEFInd....

Will this work, or am I obviously in way over my head? Will I need to do further repairs to disk 2? Will rEFInd see both OSs correctly? Can I/should I uninstall bootcamp from win8.1? Are there vital missing steps?

Or (most likely) is there nobody in the free world who could predict the consequences of such rash actions?

thanks for any tips!
-eric

 

Well, since someone is listening....

Is there a reliable way to get two NTFS partitions on my second disk, one of which will boot windows?

I have no real data to lose, just a lot of installation time.... so I can wipe the drive if need be.

 

Well, as I posted elsewhere on these forums, I did get this working. I have both windows8.1 and OSX booting via efi on my ssd. And I have a third NTFS partition for my data. There's no hybrid boot, so I can repartition and update with no hassles.

I DID however have an unbootable mac at one point, due to reformatting both drives!!! Between internet rescue and testdisk I got everything back though.

cheers,
-eric