Boot to the Windows 7 installation DVD.Formatted the disk intended for Windows 7 as Mac OS extended (Journaled) with Guid Partition Map in Apple’s Disk Utility for the fun of it.It would have been much easier with a 2TB drive. There’s no shortage of blog post hacks out there describing methods of how to install Windows 7 on old Mac Pros. If you attempt to format a 3TB drive MBR using the Apple Disk Utility in High Sierra, you’ll get the error message “The disk is too large to be supported by the given partition scheme. The selected disk is of the GPT partition style”. If you formatted it with Apple’s Disk Utility, you might get the following error message when trying to install Windows: “Windows cannot be installed to this disk. To install Windows 7 on this old Mac Pro, the drive needs to be formatted with a MBR partition scheme. The third 3TB drive was to be added to the macOS installation as a data disk. The goal was to install Windows 7 on the second 3TB drive. We did a fresh install of High Sierra on the first 3TB drive. We recently had a Mid 2010 Mac Pro in the shop which had three 3TB hard drives.

Installing windows on mac tower