I am currently running Mac OS X Version 10.4.11 (Tiger) on a MacBook. My MacBook came with Leopard, but we bought if off eBay, so when I had to re-install the OS software (for reasons that are not pertinent), it went back to Tiger. I am unhappy with Tiger for various reasons, and would like to go back to Leopard. I do not want to pay the 100-odd dollars to buy Leopard from Apple or from eBay, because I'm only 16 and jobless so I don't have that kind of money. My friend has an iMac and another friend who just got a new MacBook Pro, and I'm not sure the exact version of Leopard they have, but if I used their disks to update my MacBook, would it work? If you need anymore information, please tell me. Thank you!