C++ doesn't have a standardised binary interface. The compiler "mangles" each symbol name (i.e. each function or static data) to include information about namespaces and signature, so that namespaces, argument overloading, &c. can work. Each compiler is free to decide how to do this. Different MSVS compiler versions do name mangling in different ways, so in general you can't link a C++ library compiled with 2005 and a library compiled with 2008 together: this includes loading a 2008 DLL from a 2005 executable (for example). You can do this if the interface between the libraries is C, as long as the relevant functions are marked with
extern "C" to prevent name mangling. And in practice the differences are not always that great: for example, I never had trouble using VS2005 SP1 to compile a library for 3ds Max 9, which supposedly requires VS2005 with no service pack.
Microsoft is trying to fix this incompatibility, so in VS2010 they introduced an option, so VS2010 can produce binaries compatible with VS2005 programs or VS2008 programs (maybe some earlier versions too, I forget). If you have to create a plugin to work with multiple 3ds Max versions, and you don't get caught out by any VS2010 bugs, this is probably a good option. Also, the Intel C++ compiler has a mode where it produces binaries that are compatible with an MSVS version of your choice, which might be a better option for you if it's for hobby use or you can afford the slightly expensive price tag. (They achieve this by copying the way MSVS does name mangling.)