I'm starting out with Visual Studio 2005. I have an application that worked fine with the Borland bcc32 compiler, but when I compile with VS I get several errors telling me that this or that constant is undefined. Checking the header files I found that these constants are conditionally defined depending on the value of _WIN32_WINNT. A simple test program compiles under bcc32 and VS tells me that _WIN32_WINNT is defined as 0x501 under bcc32 and undefined under VS. I'm running Windows XP, so I assume _WIN32_WINNT should be defined to the right value. How do I make sure this is so. I could explicitly define it in my code, but this ought not be necessary. Any help would be appreciated.