C GUI library ??

Such libraries are exist for C++, namely wxWidgets,FLTK, etc.
Are there such libraries for C ?

There is GTK+.
Many of the others, like Qt and Tk, are not primarily targeted to C but nevertheless have C bindings available.

err .. I mean the library for Windows & statically linkable ...

The Win32 API is a C library and includes GUI functions. Not enough?

Good point, SMurf

All libraries and wrappers finally would have to convert their own functions to Win32 functions anyway. Then why use them?

Because you gain better cross-platform portability, of course. WINE is all very nice, but it's really a crutch.

He said, he wants it for windows.

Then he uses wrappers. They are easier and faster to code in.
You are never going to give up bringing this issue over and over, and over, again. Are you max?