MacBook Pro 15 inch mid-2010 install dual bootcamp - High Sierra OSX plus Windows 10 plus Windows Vista

Solution 1:

The short answer is that you do not want to attempt what you are trying to do. At this point, I would recommend concentrating on undoing any damage that you might have caused by the steps you have already taken. You should edit your question and post the output from the following commands.

diskutil list
sudo gpt -r show /dev/disk0
sudo fdisk /dev/disk0

Note: You will have to disable System Integrity Protection (SIP) before entering the gpt and fdisk commands.

The above command will not change your disk. The command just output the current state of the internal disk partitioning. Also, I have assumed you have just one internal drive.

The more complex answer would be the following. Yes, you could have Windows 10 installed in one primary partition and then install Vista in another available primary partition. This could be set up as a dual boot arrangement. (This dual boot arrangement is unrelated to the dual boot between macOS and Windows.) However, I would first install Vista without a dual boot arrangement. In other words, to switch between Window 10 and Vista you would have to manually change to active partition. If you still wish to install Vista (I assume your Mac is Vista compatible), then I would still want to see the output from the commands given above.