To modify the macros, in a header file, add the following lines:
#define WINVER 0x0500
#define _WIN32_WINNT 0x0500
This will target the Windows 2000 operating system. Other valid values include 0x0501 for Windows XP, 0x0502 for Windows Server 2003, and 0x0600 for Windows Vista.
You can also define this macro with the /D compiler option; see /D (Preprocessor Definitions) for more information.
For more information on the meanings of these macros, see Using the Windows Headers.