It won't work. Snow Leopard will not have the drivers for the newer hardware. It's usually not possible to run any version of Mac OS X older than the one shipped on the Mac. The just-released mini will not run anything earlier than OS X 10.8.2 (and that only the build shipped on the mini). If you need to run Snow Leopard, you'll either buy an old model of Mac, or set Mac OS X 10.6 Server and run it in virtualization (VMWare, Parallels, VirtualBox).
There's an overview of the process using VMWare here:
Parallels and VirtualBox would be similar. It will provide the ability to run most PowerPC applications, though not all will work. Any that would try to write directly to the hardware (as does some communications software, for instance, or many OS/hardware utilities) will fail.
My understanding is that VMWare Fusion 5 and all versions of Fusion (other than 4.1) will NOT run Snow Leopard client; although you can install Snow Leopard Server into all of those versions.
Fusion 4.1 is quite prized and very rare to find; for the reason that it did allow Snow Leopard client to be installed. Updates removed this capability both before and after SL's installation. As I do not use Fusion, I do not know if version 4.1 survived the upgrade to Mountain Lion.
The link I posted in the post just above this one has full installation instructions for Snow Leopard (and Rosetta) into Parallels.
What PPC applications do you need to continue to run?
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OK. Well, here's the situation: I have a G4 flat-panel iMac that won't start when I press the power button. It just won't power on at all, so I'm guessing it's a power supply or switch, and I'm assuming that the hard drive w/ 300 GB of data is fine.
I should have upgraded to a Snow Leopard computer a couple of years ago in order to take advantage of Rosetta, but I didn't. So now I need a sort of stop-gap measure to run all my old apps (MS Office w/ Entourage, Photoshop, CiphSafe, MacJournal, and a kajillion others) until I can update them to Intel versions and make the leap to Mountain Lion. I like the idea of purchasing a new Mac Mini, but I need Rosetta.
I guess I could also try to find a used 2009 era Mac Mini, but I'd rather put the money toward a new one if I could somehow either install Snow Leopard client install disk (which doesn't seem possible) or run it in virtualization. I've read several conflicting reports about the ability of Snow Leopard client (that I recently purchased from Apple) being able to run in virtualization. I'm basically just trying to figure out the best way to migrate from my dead iMac to a Snow Leopard computer.
There is no "perfect" solution to your problem.
There is a thread on this forum about how to get the 2011 Mac Mini to run Snow Leopard with amazing work by Newfoundglory:
Installation of Snow Leopard Server is actively supported by all of the virtualization companies. While it sold originally for $499 from Apple; you can now find it for about $125 or less on eBay.
Installation of Snow Leopard client is not actively supported by any of the virtualization companies (with the sole exception of v4.1 of VMWare Fusion, which is now hard to find for obvious reasons and then can NOT be upgraded or this capability is lost).
These practices by these companies are a part of the common Urban Myth that the Snow Leopard EULA prohibits the virtualization of Snow Leopard in Lion or Mountain Lion.
I have posted detailed instructions on how to install Snow Leopard into Parallels at this link:
While it is not as easy to install as Snow Leopard Server, it is certainly doable and many successes are cited in that thread. If you decide to go that route. let me know over on MacRumors and I am happy to help you out!