This is the Mac disk image that contains the Mac partition from the install CD. It has the MacOS tools that allow you to boot into BeOS. Either run the "BeOS Launcher" app, which will restart the machine into the BeOS boot loader, or drop the "_OS Chooser_" extension into the Extensions folder inside your MacOS 7/8 System folder. When you boot and the extension loads, it will give you a window allowing you to choose between BeOS and MacOS.