Hi, I am facing issue compiling latest postgresql-8.3.4 code on windows .I installed Visual Studio 2005 Express and Microsoft windows SDK latest v6.1 on windows XP (SP2) as described by http://www.postgresql.org/docs/8.3/static/install-win32-full.html and trying to build postgresql-8.3.4, it is giving the following error message i.e. .\src\backend\libpq\pqcomm.c(389): error C2065: 'IPPROTO_IPV6' : undeclared identifier Microsoft SDKs\Windows\v6.1\Include\ws2def.h (407) : IPPROTO_IPV6 requires _WIN32_WINNT grater than 0x0500 i.e. #if(_WIN32_WINNT >= 0x0501) IPPROTO_IPV6 = 41, // IPv6 header … … #endif//(_WIN32_WINNT >= 0x0501) src\include\pg_config_os.h (7): That is being copied from src\include\port\win32.h . It set _WIN32_WINNT to 0x0500 i.e. #define _WIN32_WINNT 0x0500 I removed the following line from src\include\port\win32.h(7) #define _WIN32_WINNT 0x0500 and it started building successfully and regression is working fine too. In the Visual Studio 2005 Professional "IPPROTO_IPV6" was defined in WinSock2.h and it is without any condition. In the latest SDK v6.1 condition _WIN32_WINNT >= 0x0501 is added around IPPROTO_IPV6 ( http://msdn.microsoft.com/en-us/library/ms738574(VS.85).aspx ).IPV6_V6ONLY is also used in the .\src\backend\libpq\pqcomm.c(386) that is for Vista or Win2008. It means that IPV6 cannot be used for building Windows 2k (_WIN32_WINNT == 0x0500) applications when using Windows SDK v6.1 or higher. http://www.microsoft.com/technet/network/ipv6/ipv6faq.mspx Microsoft has no plans to provide supported IPv6 protocol implementations for Windows 2000, Windows 98, and older versions of Windows. Best Regards, M Asif Naeem _________________________________________________________________ Invite your mail contacts to join your friends list with Windows Live Spaces. It's easy! http://spaces.live.com/spacesapi.aspx?wx_action=create&wx_url=/friends.aspx&mkt=en-us