Fltk1.1 with MinGw?

I have a project that compiles in linux and I am now trying to compile it under MinGw in Windows 7. The project includes the fltk library. When I try to compile, I get the message that the FL/Fl.h file is not found -

GUIWindow.h:5:18: fatal error: FL/Fl.H: No such file or directory 
compilation terminated 

I downloaded the fltk 1.1 files and extracted them to my desktop. I went into the directory, configured, and compiled the files successfully. So what am I missing here to get this to install? I thought that with #include<>, if the library is installed correctly that it will find the files no matter where they are at.开发者_运维问答 So what else is necessary under MinGw? Any help is appreciated.

Okay well I just cut the FL folder from the fltk folder and put it in MinGw/include. This compiles. If anyone can explain why just having #include works in linux but not in MinGw, I would be grateful.