If the mouse is over the window, it will receive WM_LBUTTONUP, if the mouse is outside - it will not. To overcome this situation, you need to 'SetCapture' on WM_LBUTTONDOWN and 'ReleaseCapture' on WM_LBUTTONUP...

Try to change write and read modes to binary L"wb" and L"rb"

I would like to know more about what you are offering (Project neeed to be done, deadline, fee). Write me at 'romualdas_cukuras@yahoo.com'