I restored the mavericks bootable on a HDD partition. To do so I used my friends MBP which runs mavericks as well, since my leopard machine couldn't handle it, dont know why ? Once I prepared this bootable HDD, tried it on again my friend's MBP and the installation screen came up as I wished. However, when I tried it on my leopard Imac, it didn't. On the selection screen ,which shows up upon pressing and holding alt key, I chose the HDD to boot, then the Apple logo appear and then my desktop showed up instead of ending up with the installation screen. What is wrong ? Why it doesn't work as it worked on MBP ??