Your mouse cursor will probably be trapped inside the virtual machine. Press the right Ctrl key on your keyboard to allow your mouse to escape. Then, at the bottom right of the virtual machine screen, right-click on the little CD icon, and click Choose a virtual CD/DVD disk file. A Windows Explorer window will pop up; from there, select the OS X 10.8 Mountain Lion bootable DVD.
Create a Bootable OS X 10.8 Mountain Lion USB Drive - A detailed ArsTechnica piece to create a bootable OS X 10.8 "Mountain Lion" USB flash drive for a Hackintosh (or a Mac) using the helpful DiskMaker X app.
OS X 10.8 Mountain Lion bootable DVD for Intel PCs by Olarila
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