When you build an MFC project from a previous release in Visual C++В .NET, you may see compilation errors because your project is now using a different value for WINVER.
When your project was being built in a previous version of Visual C++, WINVER may have been set to 400, to allow compilation using an earlier version of Platform SDK header files, such as may have been found on Windows 95 or Windows NT 4.0.
You may have implicitly gotten your WINVER=400 setting in one of two ways:
By using the earlier version of the Platform SDK header files that were available with the earliest versions of Visual C++ 6.0.
By including winres.h in your Visual C++ 6.0 project. This file contained a definition of 400 for WINVER.
If you got your WINVER=400 setting by either of these means, if you still need WINVER=400 to be set, and if your project is now getting compiler errors in Visual C++В .NET, you need to explicitly define WINVER=400. For example, in a header file, you could add the following line:
#define WINVER 0x0400
You can also define this macro with the /D compiler option; see for more information.