When building gambit-c in linux and enabling cplusplus, I could place "Using namespace std;" in c-declare forms and also declare c++ class types, using anything c++. However, with the free visual c++ build, I cannot. I assumed this was because visual c++ is assuming that all the files are c and is thus using a c compiler instead of a c++ compiler. So when I compile my scheme files it assumes it is c and won't allow c++.