Don't include Windows.h -  I had to say it.  ;)

Always have a blank line at the bottom of each source or header file.  You get g++ compiler warnings if files don't have an extra carriage return at the bottom.

Compiler pragma warning disable statements should be ifdef'd for WIN32 only.

#include statements must match the case of the header file name.

#include "gpireader.h" // won't compile on g++, but

#include "GPIReader.h" // will compile on g++

Don't forget to use virtual destructors where appropriate, g++ will complain if they're missing.

Don't memset STL strings (std::string) to zeros.  Strange and odd memory corruption will occur if you do.

Don't memset structs which contain STL strings, see point above.

Don't include enum names. 

if (res == ResourceType::AccessBlock) // won't compile on g++, but

if (res == AccessBlock) // will compile on g++

Don't include the class prefix in header files for method declarations.

std::string GPIReader::GetXMLStringResource(ResourceType type);  // won't compile on g++, but

std::string GetXMLStringResource(ResourceType type); // will compile on g++

stricmp (case insensitive strcmp) function is not available on Linux, you must toUpper then compare or something.