I have a USB with Mountain Lion 10.8.2 which is bootable. I use this on my Macbook Air and it plays fine. Now, I try to format my new iMac using this USB. But get the message that it is not compatible with your computer. For me, the new iMac just delivered with the precise 10.8.2, so I do not know why I am not allowed to do this? The reason it is so important to have a USB stick is that Apple's restore system stinks and is all criticism. Last time I used it, it took 4 hours with a 112Mbit internet connection to format a computer while a usb it takes max 30 min. Anyone have any know-how why I can not use my stick on this machine.?