The problem with the application not being able to instantiate the MAPI.SESSION is that I had to register the CDO.DLL module to XP. However, I encountered problems with the regsvr32 program, because the dll referenced the following two modules that were not in the system library:
gapi32.dll
efsadu.dll
I identified these references using the DependencyWalker utility. Once I downloaded the missing modulesinto my windows folder, the registration program ran sucessfully, and my application is now able to create the MAPI.SESSION object.