I would recommend just installing Windows 7 as you would with Windows 8 +.
Substitutes:
Hold down the option key while turning on your computer instead of using refind, this will give you a boot menu.
Uncheck all the options in boot camp, except the option to install drivers to a usb stick.
Go to disk utility, make a new partition, and set it to MSDOS FAT.
Start up your Mac, booting from the usb stick(hold down option key while turning on your computer). When prompted for an install disk, choose the partition you made. Go through the rest of the install process, and then plug in your driver usb. Find the setup.exe, and go through the it's install process.
Then you should be all set.
With respect to Microsoft Windows, 2012, through 2014 were translational years for Apple Macs. For the 2011 and older Macs, Windows is installed in BIOS/MBR mode using a Windows installer DVD. In 2012, Apple started to drop the optical drive from its Mac models. To allow Windows to be installed, the Boot Camp Assistant application copied the files from the Windows installer iso, to a USB flash drive. The "Boot Camp Support Software" was also included on the flash drive. To install older Windows versions, the "Boot Camp Support Software" files had to be manually copied to the flash drive.
Staring in 2015, Apple dropped the ability to install operating systems that require a BIOS/MBR boot method. This eliminated the possibility of installing Windows 7 on these Mac models. This change brought Macs update to date with the reset of the industry, which converted to EFI/GPT booting of Microsoft Windows in 2011. Also, with the release of El Capitan (OS X 10.11), the Boot Camp Assistant can now install Windows on certain Mac models without the use of a DVD or USB flash drive.
So where does this leave the transitional 2012 through 2014 model year Macs? I wish I had an absolute answer. Consider the following.
- If one had Windows 7 installed in BIOS/MBR mode and upgraded to
Windows 10, then the result would be Windows 10 running in BIOS/MBR
mode using the "Boot Camp Support Software" intended for a Windows 7
installation. Some people have reported that running "Apple Software
Update" afterwards will result in the downloading and installing of
newer "Boot Camp Support Software".
- Some people have installed Windows 8/8.1/10 from scratch on their
model Mac in BIOS/MBR mode with any problems, while others have
done the same on their model Mac in EFI/GPT mode without problems.
I do not remember anyone trying both methods. Usually, once one method
works, they quit trying.
So, it really depends on what the "Boot Camp Support Software" for you model Mac will allow. You have reported that the Boot Camp Assistant installed Windows 10 on your Mac using a BIOS/MBR boot method. So I assume this is what is right for your model Mac. However, if you have created the Windows 10 USB flash drive installer, then you could try both methods. Insert the flash drive and restart the Mac. Hold down the option key at startup. If an icon labeled "Windows" appears you can try a BIOS/MBR install. If a icon labeled "EFI Boot" appears, then you can try a EFI/GPT install.
In the end from the user perspective. it really does not matter which method is employed to boot Windows. Ubuntu is installed in EFI/GPT mode which works independent of either Windows boot method. I guess the Windows EFI/GPT method offers a fast boot option, but this can only be used when Windows is the sole operating system on a computer. You intend to include both OS X and Ubuntu Linux.
Note: Some Linux installers will not install in EFI/GPT mode to a hybrid GPT. To solve this problem, you may need to:
- (Optional) Make a backup copy of your Protective MBR (PMBR).
- Use the Boot Camp Assistant, Disk Utility or other application(s) to
create a hybrid GPT.
- Install Windows. (Usually to partition 4)
- Save a copy of the hybrid MBR.
- Covert the MBR back to a Protective MBR (PMBR) or restore from backup.
- Install Linux to new partitions without changing the existing partitions.
- Restore the hybrid MBR from the backup.
Another solution, would be to install Linux first, leaving a space for Windows to be installed after Linux. In this case, format the Windows partition HFS before installing Linux and FAT before installing Windows.
If you intend to install Windows on a second disk, you may want to read the posts made to the question: "Problem Installing Windows 7 via Boot Camp".
Best Answer
Steps to a Create USB Windows 10 Installer
Use to Disk Utility application to erase a 16 GB or larger USB flash drive. Use the setting shown below.
Use the Finder application to mount the Windows 10 iso file.
Use the Finder application to copy all the files from the mounted Windows 10 iso file to the USB flash drive.
Use the Finder application to copy the downloaded Windows Support Software to the USB flash drive.
Below is the results from a Windows 10 (1909) download and the Window Support Software for a 2018 mac mini.
Procedure to Install a Second Windows 10 Operating System
Boot from the USB Windows installation flash drive. Proceed until you reach the same screen as shown in the image below. Click on
Custom: Install Windows only (advanced)
.The next screen should be similar to the one shown below. At this point, press the shift+F10 key combination to open a Command Prompt window.
The next image shows an opened Command Prompt window.
You need to shrink the Windows partition to make room for the second Windows installation. This can be down by entering the following commands in the Command Prompt window. In this case, commands will shrink the Windows partition (number 3) by
70000
MB (which is 70 GB). You may wish to use a different value.Below is an example output from entering the above commands.
After the Command Prompt window closes, you will need to click on the
Refresh
button. The result should be similar to the image shown below.Next, highlight the
Drive 0 Unallocated Space
, then click on theNew
button. Enter 315 for Size and then click on theApply
button. The result should be similar to the image shown below. Here, a new unformatted primary partition (number 4) was created for future use as an EFI partition.Again, highlight the
Drive 0 Unallocated Space
, then click on theNew
button. Without changing the Size, click on theApply
button. When the popup shown below appears, click on theOK
button.The image below shows a 16 MB Microsoft Reserved partition (number 5) was create along with a new primary partition (number 6).
With the new primary partition (number 6) highlighted, click on the
Next
button. When the popup shown below appears, click on theOK
button. The Windows installation should proceed. This new primary partition will be automatically NTFS formatted before being using as the location for the second Windows installation.