m_objTransformation is actually pointing to an instance of a SM3DDisplayTransformationClass
object. That is why the exception is complaining about casing from SM3DDisplayTransformationClass to I3DDisplayTransformationSetup. This is legal though as SM3DDisplayTransformationClass implements I3DDisplayTransformationSetup, or the compiler would have moaned
SM3DDisplayTransformationClass by law must always be able to cast to one of its interfaces ,surely!
there are more than a few differences between CE and desktop windows OS stuff so I would really look to see if that code can be found or if a native win32 version of the dll can be found.
you might (depends on the rest of the code in it) find other problems if it was written for CE and never tested on a desktop before.
Hope it goes well and that I am just adding a caution note.
WIth .Net CF 1.xx we always say "Net CF is just a thin wapper around SystemNotImplimentedExeption" NetCF 3.5 is WAY better than 1.x