By ordering the lines, it can be easier to check which headers are included.
That makes sense, but keep in mind Manos' point (although normally the order shouldn't matter - if you have redefinitions, then the header files need to be controlled).
Anyway, attached a simple exe that sorts the clipboard. It asks for confirmation to replace the clipboard with its sorted version.
Assembler source is included, *.asc = *.rtf, opens inter alia in WordPad and MS Word.