Downgrading to Snow Leopard

[JSchwartz15]

I currently have a 2010 MacBook HD inside a Mid-2012 MBP. It was running Yosemite. I've wiped the HD with Disk Utility and using Recovery Mode installed Mountain Lion so it's running as a new machine. I have inserted a Snow Leopard Install Disk into the computer and I'd like to know what steps I have to take to get the computer to run it. I need it to run some PPC stuff.

 

[DeltaMac]

I currently have a 2010 MacBook HD inside a Mid-2012 MBP. It was running Yosemite. I've wiped the HD with Disk Utility and using Recovery Mode installed Mountain Lion so it's running as a new machine. I have inserted a Snow Leopard Install Disk into the computer and I'd like to know what steps I have to take to get the computer to run it. I need it to run some PPC stuff.

Nope.
Your mid-2012 MBPro is too new to boot with Snow Leopard.
It makes no difference if the hard drive came from an older system. You still need to have a system installed that your MBPro will boot, and that will be Lion or newer.
There is another possibility, such as installing Snow Leopard Server as a virtual machine in Parallels - but you can't do that with the Snow Leopard normal system.

 

[JSchwartz15]

Nope.
Your mid-2012 MBPro is too new to boot with Snow Leopard.
It makes no difference if the hard drive came from an older system. You still need to have a system installed that your MBPro will boot, and that will be Lion or newer.
There is another possibility, such as installing Snow Leopard Server as a virtual machine in Parallels - but you can't do that with the Snow Leopard normal system.

Is there anything I can do in Terminal to trick the system?

 

[AlecZ]

Is there anything I can do in Terminal to trick the system?

I don't know the specifics, but yes, there's a way to trick it. It may not work 100% correctly. Someone here simply installed it on the hard drive using an older Mac that was qualified to run SL, but I don't know if that will work for your computer. I remember there being a good thread on this, but I can't find remember what it's called.

 

[chabig]

You can run Snow Leopard in a Virtual Machine environment like Parallels.

 

[Intell]

I don't know the specifics, but yes, there's a way to trick it. It may not work 100% correctly. Someone here simply installed it on the hard drive using an older Mac that was qualified to run SL, but I don't know if that will work for your computer. I remember there being a good thread on this, but I can't find remember what it's called.

That method will not work for a 2012 Macbook Pro. Those will only boot with what they originally shipped with.

You can run Snow Leopard in a Virtual Machine environment like Parallels.

It should be noted that due to the restrictions set forth by Apple and the virtual machine developers, you can only run Snow Leopard Server in a virtual machine without making unauthorized and unethical modifications to the virtual machine.

 

[JSchwartz15]

Ok, so I've done some more work and I'd like to know if it's possible for me to move forward from here: I have turned the old HD into an external, and partitioned it with one partition with a Apple Partition Map scheme, not GUID. I tried to use the Snow Leopard disk I have but it wouldn't let me open the installer. I then tried a Leopard disk and the installer launched successfully, but when restarting the computer had a kernel panic error

 

[Intell]

That model Mac cannot boot from an APM formatted disk, nor can it boot from Leopard or Snow Leopard.