Dear William E. Kempf, I installed the latest version of the boost-1.31.0 on Win xp pro with vc7.1 and tried to use the thread library. During the first build of several samples, MSVS(vc71) gave me a warning about the errors. However I ignored the errors and select option to proceed(the same result is in other case). It seems to me the samples work correctly in spite of errors and warning located below my message. I had no warning or errors on the next build of the same sample at all. Would you please tell me what is going on? And how do I fix it? Thanks Valery Salamakha VC71_ROOT\include\stdexcept(14): see declaration of 'std::logic_error' c:\Boost\include\boost-1_31\boost\thread\exceptions.hpp(28) : see declaration of 'boost::lock_error' c:\Boost\include\boost-1_31\boost\thread\thread.hpp(78): warning C4251: 'boost::thread_group::m_threads' : class 'std::list<_Ty>' needs to have dll-interface to be used by clients of class 'boost::thread_group' with [ _Ty=boost::thread * ] c:\Boost\include\boost-1_31\boost\thread\mutex.hpp(36): warning C4275: non dll-interface class 'boost::noncopyable' used as base for dll-interface class 'boost::mutex' c:\Boost\include\boost-1_31\boost\noncopyable.hpp(22) : see declaration of 'boost::noncopyable' c:\Boost\include\boost-1_31\boost\thread\mutex.hpp(35) : see declaration of 'boost::mutex' c:\Boost\include\boost-1_31\boost\thread\thread.hpp(38): warning C4275: non dll-interface class 'boost::noncopyable' used as base for dll-interface class 'boost::thread' c:\Boost\include\boost-1_31\boost\thread\thread.hpp(67): warning C4275: non dll-interface class 'boost::noncopyable' used as base for dll-interface class 'boost::thread_group' c:\Boost\include\boost-1_31\boost\noncopyable.hpp(22) : see declaration of 'boost::noncopyable' c:\Boost\include\boost-1_31\boost\thread\mutex.hpp(114): warning C4275: non dll-interface class 'boost::noncopyable' used as base for dll-interface class 'boost::timed_mutex' c:\Boost\include\boost-1_31\boost\noncopyable.hpp(22) : see declaration of 'boost::noncopyable' c:\Boost\include\boost-1_31\boost\thread\mutex.hpp(113) : see declaration of 'boost::timed_mutex' c:\Boost\include\boost-1_31\boost\thread\mutex.hpp(74): warning C4275: non dll-interface class 'boost::noncopyable' used as base for dll-interface class 'boost::try_mutex' c:\Boost\include\boost-1_31\boost\noncopyable.hpp(22) : see declaration of 'boost::noncopyable' c:\Boost\include\boost-1_31\boost\thread\mutex.hpp(73) : see declaration of 'boost::try_mutex' c:\Boost\include\boost-1_31\boost\thread\exceptions.hpp(29): warning C4275: non dll-interface class 'std::logic_error' used as base for dll-interface class 'boost::lock_error' c:\Boost\include\boost-1_31\boost\thread\exceptions.hpp(35): warning C4275: non dll-interface class 'std::runtime_error' used as base for dll-interface class 'boost::thread_resource_error' c:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include\stdexcept(136) : see declaration of 'std::runtime_error' c:\Boost\include\boost-1_31\boost\thread\exceptions.hpp(34) : see declaration of 'boost::thread_resource_error' __________________________________ Do you Yahoo!? Yahoo! Mail - Helps protect you from nasty viruses. http://promotions.yahoo.com/new_mail