The official #define for 32-bit and 64-bit Windows is _WIN32.

The official #define for 32-bit and 64-bit Windows is _WIN32.

It's _WIN32, with a leading underscore, not WIN32.  See, for example:

	https://sourceforge.net/p/predef/wiki/OperatingSystems/

and

	https://msdn.microsoft.com/en-us/library/b0084kay.aspx

*Some* environments may also define WIN32, but we shouldn't depend on
that.