KDE 4.x
 

How do I prevent KDE from shrinking screen windows when I move the mouse? There doesn't seem to be any consistent pattern; it just happens often and it's annoying.

You mean the "present windows" effect that is by default activated when you slide your cursor to the top left corner?
You configure it in Workspace behaviour->Screen Edges.

If this isn't what you're looking for, you'll have to be more specific about your problem.

Serafean