Downgrade pre-installed Lion to Snow Leopard on a 2011 Macbook Pro?

I have very recently purchased a Macbook Pro pre-installed with Lion. After spending several days unsuccessfully trying to get it to play nicely with Active Directory I purchased a retail copy of Snow Leopard, booted it from an external DVD drive (wouldn't read the disc) erased the HDD and attempted to install Snow Leopard. No go. Forums suggest it cannot be done. I now have a blank HDD.

Has anyone successfully downgraded from Lion to Snow Leopard on a pre-installed Lion system? If so, can you give instructions or point me in the direction of how to do this please?

I'm not sure if this will work in your case. But I have a 2010 MacBook Pro I cannot install the retail copy of Snow Leopard onto. That retail disc is 10.6.3, and the laptop needs a higher version.

To overcome this, I installed Snow Leopard on an external drive connected to an older Mac. I then updated Snow Leopard to 10.6.8 and copied the contents of that drive back to my MacBook Pro via SuperDuper.

Now, in your case, I'm not sure if Snow Leopard will work at all on the recent MacBook Pro. But, if you have access to an older Mac, give my solution a try.

Although in general running an older OS than what ships is not something that works, during the transition there is often more leeway for the drivers needed to be in a late enough version

Since you just bought a retail version of the OS - call Apple immediately and ask if they can assist to see if they need to ship a different build to you at no cost. (You usually have to pay if you lose a disc, but in this case, if the mac supports Snow Leopard there may be an install disc for that specific model or a newer pressing of the DVD may be the only thing you need.)

You can also research it here:

• Mac OS X versions (builds) for computers
• Key in your serial number here - http://support.apple.com/manuals/
• Finding your Mac OS X version and build information

Chances are you have an Early 2011 model MacBook Pro, but it pays to be sure by running the serial number (and even that can be wrong - but Apple support can help in that case...)

If my guess is correct, you just need 10.6.6 and a build of 10J3210 or newer. I haven't seen a retail Snow Leopard disc that is newer than 10.6.3 Build 10D575 so you may need a newer build to get going.

Armed with this information, you now can understand why "Retail copies of Mac OS X may not always work properly with new Macs" Do call Apple Care and see if they can and will get you a machine specific build since you are a paying customer :-)