minecraftiaMACUser100 wrote:
The problem with this is that Windows WILL NOT install onto the disk because it needs MBR on the destination disk,
having MacOS 10.8.5 on one partition and MacOS 10.13 on another partition, and Bootcamp not even trying to do anything when there are already 2 partitions. I'm trying to install Windows on a 3rd partition.
trying to simply reinstall it on that same partition would say that the disk is "of the GPT partition style". Whoever made this a thing needs to go under the jail, but I really need to do this. Any ideas?
I had to remove a bunch of text from your earlier post here in order to even make sense of the situation. It appears you have a Mac model from around Late-2009 to 2011 based on the two operating systems you mention.
Bootcamp Assistant was only designed to be used with one macOS installation on the internal drive.
If you insist on wanting two macOS installations and a Windows installation, then you will need to learn about the hybrid partition scheme used by Apple. Perhaps there is some older documentation online somewhere which will give you some clues. You can also experiment with installing just one Apple OS and using Bootcamp Assistant to install Windows, then closely examine the drive layout so you can try to recreate that layout manually. More than likely you will need to familiarize yourself with the command line and various command line utilities as well.
I'm not certain, but I don't think macOS has used hybrid partition layouts for some time now so it is doubtful you will find anyone who is able to assist you since they would also need an older system & access to an older version of Windows which requires a valid license key (AFAIK, Microsoft turned off the activation servers for older versions of Windows). Sometimes you just have to dig in and perform the research & analysis yourself.
FYI, your best option to installing Windows onto a GPT partition is probably Windows 7 since it should support both GPT partitions and UEFI booting which should make things easier since a Mac's firmware is very basic and is meant mainly to be used with macOS. I don't know how you can use a legacy MBR bootloader on a Mac since that must be some of that Bootcamp Assistant secret magic sauce. I've managed to figure out a lot of boot issues with various operating systems over the years, and I have no clue how this would be done. It has to be some special Apple utility provided by Bootcamp Assistant.
Another option would be to install just one version of macOS onto the internal drive and use Bootcamp Assistant to install Windows. Then install the 2nd macOS onto an external drive. Yes, the external drive will boot & operate slowly due to the USB ports, but it may suffice depending on how you utilize that 2nd macOS. Or perhaps you can run the 2nd macOS in a VM.
Keep in mind people who successfully installed Windows on a Mac without using Bootcamp Assistant probably did so without any existing macOS installation or they only installed later versions of Windows which supported both GPT partitions and UEFI bootloaders.
Either you will need to do the research & work to figure it out on your own, or you will need to ask those people who you say successfully installed Windows onto a Mac without using Bootcamp Assistant as one of the other contributors already suggested for the latter option. Obviously no one who has seen this thread has ever tried it.