Just bought a second-hand 2011 27 inch iMac. (I currently have a 2009 24 iMac) I want to wipe it completely and install the latest version of mountain lion (it currently has 10.7.5 on it and the seller did not include any installation disks). I'd like to use my Apple ID to download mountain lion directly onto the machine, but the instructions say that I need to erase the disc first to do a clean install. However, this isn't possible as it is the start-up disk and there are no partitions. I'm currently using my 2009 24 inch iMac as my main work machine. Can I: 1. Download the mountain lion installer from the App Store to my 2009 iMac (without installing it here!). 2. Connect the two machines together in target mode and install Mt lion from the 2009 iMac to the 2011 iMac. Is this possible? I can't think of any other way of doing it as I don't have any kind of installation disks. The 2009 iMac only has a snow leopard installer (somewhere). Any thoughts greatly appreciated.