   Linker Error:Unresolved external symbol
  hi,..i am trying to compile source code from "Programming Game AI by Example" in Visual Studio 2005 on Vista x64.and i am getting the following error:main.obj : error LNK2001: unresolved external symbol "public: virtual void __thiscall BaseGameEntity::Render(void)" (?Render@BaseGameEntity@@UAEXXZ)1>main.obj : error LNK2019: unresolved external symbol "protected: __thiscall BaseGameEntity::BaseGameEntity(int)" (??0BaseGameEntity@@IAE@H@Z) referenced in function "public: __thiscall Miner::Miner(int)" (??0Miner@@QAE@H@Z)1>main.obj : error LNK2019: unresolved external symbol "public: void __thiscall MessageDispatcher::DispatchDelayedMessages(void)" (?DispatchDelayedMessages@MessageDispatcher@@QAEXXZ) referenced in function _main1>main.obj : error LNK2019: unresolved external symbol "public: static class MessageDispatcher * __cdecl MessageDispatcher::Instance(void)" (?Instance@MessageDispatcher@@SAPAV1@XZ) referenced in function _main1>MinerOwnedStates.obj : error LNK2001: unresolved external symbol "public: static class MessageDispatcher * __cdecl MessageDispatcher::Instance(void)" (?Instance@MessageDispatcher@@SAPAV1@XZ)1>MinersWifeOwnedStates.obj : error LNK2001: unresolved external symbol "public: static class MessageDispatcher * __cdecl MessageDispatcher::Instance(void)" (?Instance@MessageDispatcher@@SAPAV1@XZ)1>MinerOwnedStates.obj : error LNK2019: unresolved external symbol "public: void __thiscall MessageDispatcher::DispatchMessageA(double,int,int,int,void *)" (?DispatchMessageA@MessageDispatcher@@QAEXNHHHPAX@Z) referenced in function "public: virtual void __thiscall GoHomeAndSleepTilRested::Enter(class Miner *)" (?Enter@GoHomeAndSleepTilRested@@UAEXPAVMiner@@@Z)1>MinersWifeOwnedStates.obj : error LNK2001: unresolved external symbol "public: void __thiscall MessageDispatcher::DispatchMessageA(double,int,int,int,void *)" (?DispatchMessageA@MessageDispatcher@@QAEXNHHHPAX@Z)1>MinerOwnedStates.obj : error LNK2019: unresolved external symbol "public: static class CrudeTimer * __cdecl CrudeTimer::Instance(void)" (?Instance@CrudeTimer@@SAPAV1@XZ) referenced in function "public: virtual bool __thiscall GoHomeAndSleepTilRested::OnMessage(class Miner *,struct Telegram const &)" (?OnMessage@GoHomeAndSleepTilRested@@UAE_NPAVMiner@@ABUTelegram@@@Z)1>MinersWifeOwnedStates.obj : error LNK2001: unresolved external symbol "public: static class CrudeTimer * __cdecl CrudeTimer::Instance(void)" (?Instance@CrudeTimer@@SAPAV1@XZ)1>C:\Users\vrd\Documents\Visual Studio 2005\Projects\demo\Debug\demo.exe : fatal error LNK1120: 6 unresolved externals1>Build log was saved at "file://c:\Users\vrd\Documents\Visual Studio 2005\Projects\demo\demo\Debug\BuildLog.htm"1>demo - 11 error(s), 5 warning(s)========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========through googling,..i managed to find a relevant link in which it was suggested to set Code Generation Option to Multithreaded Debug DLL but it was not helpfull in my case.please help me out. thanks.   