HI, I'm trying to build boost 1.47's asio library with the BOOST_ASIO_SEPARATE_COMPILATION macro in windows 7, 32-bit, VS 2010. With this macro, the asio library can be included and built easily without building all of boost or using bjam. However, I get the following linker error: unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::system_category(void)" (?system_category@system@boost@@YAABVerror_category@12@XZ) referenced in function "public: __thiscall boost::system::error_code::error_code(void)" (??0error_code@system@boost@@QAE@XZ) unresolved external symbol "class boost::system::error_category const & __cdecl boost::system::generic_category(void)" (?generic_category@system@boost@@YAABVerror_category@12@XZ) referenced in function "void __cdecl boost::system::`dynamic initializer for 'posix_category''(void)" (??__Eposix_category@system@boost@@YAXXZ) 1> Basically the functions boost::system::system_category and boost::system::generic_category aren't defined anywhere. I can't find the implementation of these functions in boost source when I tried grepping it. Should I just use bjam to build the asio library. Thanks arun