I occasionally get this problem where for some reason small, dotted gray boxes appear around my desktop icons. It always goes away after I restart, but I'm just curious what it is. I don't know of anything in particular I do to cause it, but it only outlines icons I click, and it only does it to one icon at a time. The picture below is the box on the recycle bin. IF I click a different icon it'll happen to that one instead. I'm using windows 7.
My Computer, click
Advance System Settingsfrom the left pane, click
Settingsunder Performance. You should see a window that has full of tick boxes for adjusting various visual effects.