Interesting. But when a disk has an OS predating the one on the hard drive it still may be possible. The most salient example is Disk Warrior. These guys are never in a hurry to update the OS on their DVDs, yet their SL DVD that I just got from them boots up my MBP with Lion. True, it does not have an installer, but still...

Last edited by macnerd10; 10/14/11 06:21 PM.
Alex
3.1 GHz 13" MacBook Pro 2015, 8 GB RAM, OS 10.11.2, Office 2011, TimeWarner Cable
2.8 GHz Xeon Mac Pro 2010, 16 GB RAM, OS 10.11.2, Office 2011, LAN