I dont know if this is a bug, or me being obtuse, however, when I hit F1 to open the help file, it is always displaying "almost maximized" (I forget the terminology for it, windowed maybe??). The file works the way it should, I can search it and whatnot. I then hit the square button in the top right corner to maximize it, which it does, but if I close it and reopen it, the same thing happens again. Mirc version 7.75 downloaded from this website on Windows 11 home 22H2 OS Build 22621.2283 (if that helps).
An image can be found HERE
While the specs are different on my other machine, the same thing happens there too. Windows 7 Professional SP1 mIRC 7.75 downloaded from this website.