Pop in your Ubuntu disc and boot it. We are going to change out partition type to HFS (apple partition). Open a terminal window and type: cfdisk /dev/hda (obrati paznju na disk/particiju koju hoces pretvorit u HFS).
Select the partition you want to install OS X on, and go to "Type." Manually write in "HFS" as the type (it's not listed, but dont worry). Now write the changes to the disk by selecting "Write." Only the partition you changed will get erased.
Ili kako je Bubba rekao, uzmi disk i stavi ga u drugu masinu...ili nesto trece...