Here is the info you need to understand how the Nook Color boots and runs the operating system Gingerbread from the microsd card slot:http://forum.xda-developers.com/showthr ... ?t=1000957
(the agnostic image is about 9M, so go ahead and download and inspect it).
All the intructions to run 2.3.3 work without affecting the original operating system that is stored in the internal memory, furthermore, taking the sd card out would boot the original OS!
I am sure that the jumbo image would not work without modification due to the obvious hardware differences, but right now I would like to avoid the Nook device getting bricked by the simple experiment of using an unknown image (jumbo AIOS), which I assume to be somewhat similar to the one running in the nook color (Cynaodemod 7 Gingerbread 2.3.3 running from microsdcard), for the SoC inside both devices is similar.
It is the similarity of the platforms that increases the risk from where I stand.
It is simple curiosity really.