Windows keeps going to desktop

This seems to an intermittent problem.

Every half minute or so the window I am working in de-activates and I have to click it to highlight it again. When playing full screen games they keep dropping out to the desktop. Very annoying and frustrating.

 

I followed the link you suggested and did the selective boot etc and the
problem did not occur at all. However on going back to normal boot it
happened again. I have managed to remove the problem previously by closing
processes and thought I had found the program responsible but I was wrong.
Now I can't work out which is the problem.

Perhaps I can send you a screen shot of the processes running.

 

I really am at a loss... The problem has disappeared. I am away from home for a week. I will see what happens when I reboot and if it starts up again I will do what you have suggested.

Thanks