There are some windows and dialog boxes in windows which cannot be resized as they have a fixed, they cannot be moved or resized by moving the mouse cursor on the corner of the screen. These fixed windows does not have a minimize or maximise button normally, they only have a close button.
But still you can resize these windows which normally cannot be resized by using a free program called ResizeEnable which enables the function in windows to resize any window, there is not options you need to set, just run the executable and then move your mouse cursor to those windows corner which cannot be resized, now you will notice you can resize them.
Without ResizeEnable [ Original Window Size ]

With Resize Enable [ Stretched Window Size ]

So, it is simple application which lets you turn usually non-resizable windows into resizable windows. Most windows will respond correctly, but some may not!
[Thanks to Technixupdate]

Download Resize Enable