Well, another day, another issue... this time with trying to install Windows on my Mac Pro 5,1. I have tried a USB drive AND a DVD, which both have different issues:
- The USB drive throws the error above: "Windows could not prepare the computer to boot into the next phase of installation." This happens after everything has finished—the progress bar is nearly all the way done, and the only "checked item" missing is "Finishing Up" in the Windows setup.
- The DVD doesn't work since OpenCore Legacy Patcher boots via UEFI, while the DVD boots via BIOS, so that's completely out of the question to use the DVD. Thus, the DVD doesn't show up in the OCLP boot picker.
Any ideas why this is happening?
It's not that big of a deal if I can't fix it. I'm just wondering why the 5,1 doesn't seem to like any installation media
This is due to a weakness in the Windows installer, not the Mac or Open Core.. I guess the old EFI partitions confuses it.
I found the solution here, aided by some googling too. Turns out both the Win 10 and Win 11 installers gets very confused when a system has several disks with EFI partitions, if these are marked with partition id System, which they often are by default. So, this is not Open Core related at all (OCLP or other packages..).
The simple solution is to press Shift+F10 before selecting the drive to install to in the GUI. This brings opp the CLI. Here run diskpart. Go through all the drives in order, and select the EFI partition for each drive. If it has the partition type GUID named “System”, then change it to “Basic data partition” (Primary for short). This can be done with the command “SET ID=Value”, where you get Value by typing “help setid”. It’s a long alphanumeric string.
After doing this the Win installer never gets confused!
You can delete all partitions on the drive to install to before selecting it and pressing next (of course if you don’t keep anything on it), also the EFI partition, if any, can be deleted. The installer will make necessary partitions on it, and Open Core can boot the vanilla boot partition set up by the installer as it can boot UEFI systems.
After installation the GUIDs changed can be set back to “System” by the same tool.
After doing this I had a completely smooth installation of Win 11, it’s now running on my Mac Pro 5,1, and Open Core 0.6.1 (latest version) was used all the way, not issues. USB installer was made with Rufus. Keep in mind that Rufus creates an initial EFI boot partition that is also marked “System”, so this GUID must also be changed while going through all the drives above. “diskpart” will also show all USB drives.
How did you create the USB installer?
I recommend Rufus.
Now onto some Windows gaming with my Radeon VII..!
Enjoy!
