Apple Mac - Freezes when another monitor is positioned close to it

At home I usually use an Apple Mac, recently I've needed to do work on a separate PC in the same location. I've noticed some strange behaviour with the Mac when I position the monitor of the PC near my Mac, the result is I can move the mouse pointer, but the mouse click does not work and also the keyboard does not respond. The cursor for the keyboard actually disappears and the Mac appears to be frozen apart from the ability to move the mouse. First time this happened I thought there was a problem with it so restarted it, but all I needed to do was move the PC's monitor a bit further away. 

The monitor that is causing the issue is a standard Dell one and the distance the monitor needs to be is very close, approx 150mm from the Mac. 

How to move a window that has disappeared off-screen in Windows

I recently had a problem where I had two monitors then I starting working with one monitor. One problem I came across was one of the applications I used was last used in the second monitor area, so when I started the application (a Microsoft application) it appeared off screen in the coordinates it was last used, therefore I could not see it. Here are the steps to fix this annoying problem:

1. Click on the application in the taskbar or 'Alt'+'tab' to the application to give it the focus.
2. Then press 'Alt'+'Spacebar', this should display the popup window menu.
3. Press 'M' to enable the window to move.
4. Press the left arrow key to move the window left onto the first monitor.