Windows half screen not working, is not the monitor is a Windows system error

Question

All the answers published everywhere for this problem are completely wrong. They always are referring to the monitor. It is not the monitor. Let me explain; The whole computer screen is active and is showing a beautiful Windows 10 photo in it. But half the screen, the upper part the of the screen, is the only one working. The bottom part of the screen will show part of a folder if you move down, but is dead for anything else. How this happened? It has happened to me many, many times. You open a folder, if the folder or software is not previously maximized it will end up provoking this problem, that the bottom of the screen es there to be seen, but it will not work. Again, we know this will happen and we try to maximize all the folders and software. But if accidentally one is open not maximized, the whole windows computer is affected and the bottom of the screen becomes dead. We resolved this hundreds of times over the years by restoring Windows to a previous date in Windows Restore. But not this is not working anymore. So, our opinon is that this is an error in the Windows 10 software program. The monitor does not have to do with it. Please help.