You’ll be prompted to Enter Key or Run, because we’ll be using it once, click Run. Right-click the TransMac software icon and Run as administrator.Make sure you take off any important documents. Remember that all the data in the USB will be erased. Insert the USB drive that you’ll use to fix your installation of OS X.(Though, if you want to support the developer, you can purchase the full version.) TransMac is a paid software, but it has a 15-day trial solution, that give us more than enough time to move the DMG files to the USB drive from Windows. Download and install a copy of TransMac, which is the software that will make everything happen.Type the create partition primary and press Enter to complete.Īfter converting the USB flash drive from MBR to GPT format, you can use the steps below to create a bootable USB installation media to install Mac OS X.Type the convert GPT command and press Enter.