MauveCloud :
That's for maximizing applications. I thought you meant that Windows itself was only using the center part of the screen (including the taskbar and desktop background limited to that area). The red x button is for closing applications, not logging off. Admittedly, if you're using some sort of remote desktop software, closing the application is equivalent to logging off.
What application are you running that is starting in a small window?
I stand corrected. But, you get my point, hopefully. If I am on IE11, and am, for instance, just anywhere on Google, say, g-mail, or a bookmark, or even my bank account site, . Or, if I just installed an update and had to restart my computer, it always opens in a miniature window again. Whenever I restart my computer, it displays a miniature window which I always have to enlarge. I am wondering why it does this. I hope you understand what I'm trying to explain. I'm a rookie with PC's