I'd like to confirm that it IS possible to run Snow Leopard on a late 2011 MBP 15" without ANY FLAW although AppleCare technicians told me that it is not possible ! I did it on mine (CTO, 2.2 GHz i7) bought in fev. 2012 and had not the slightest issue since.
But from Apple side it is NOT recommended and certainly NOT supported . - But hey, my love and I have some scientific software and also Adobe products that only run smoothly on Snow Leopard and all our other Mac's in the family are on SL so I had to give it a try to stay productive. And personally, I'm not really happy with Lion, but that's an other story. - For me it's just roaring and definitely not the 'King' of the MacOs as the name suggests...
So here is what I did :
- As I couldn't lay my hands on a original MBP 15" Install-DVD from last summer (10.6.7) which should allow you to boot the MBP15" directly from it, I did a clean 10.6.7 install with my iMac 27" (iMac11,1 - i7 2.8 GHz) on an external hard drive starting from a 10.6.3 iMac install DVD and applying all the updates up to 10.6.7.
- Then I formatted my MBP internal drive in target disk mode and created 3 partitions (SL, Lion, Bootcamp).
- Using CarbonCopyCloner I cloned the clean SL installation one the first partition of the MBP, then disconnected the laptop and booted in SL.
- There was one little glitch with the splash screen resolution (not full screen) but nothing serious.
- Now I ran the 10.6.8 combo update that I downloaded before cloning and did all the software updates and another reboot.
- That done SL runs now without any problem - not one incompatibility issue in one month (would have been surprised because there were no major hardware changes from early to late 2011 MBP15").
- As next step I rebooted the MBP holding the alt-command-R keys to start from the Apple servers and did a new Internet install of Lion on the second partition.
- And last I installed Windows 7 on the third partition reformatting it using NTFS (be careful to choose the right partition - by the way there is a fourth partition : the rescue partition created by Lion you don't want to touch).
Once Win7 installed I ran the Bootcamp Assistant and did all updates.
And so now we have a nice triple boot MBP15" allowing us to use all the software we need without the slightest problem. You could probably even try a quadruple boot adding a Linux partition...
But be careful! I wouldn't bet that this method works for all new MBP and MBA so you want to make sure your model ran with SL back in summer 2011 and had no major hardware changes before trying! You can also test booting it first from an external drive with the clean install on it.
I neither do know if my method worked because the iMac 27" and the MBP15" both have a i7 Quad Core.
that's it, have fun!