Using explorer, I often highlight a few files on the right pane using control key and left mouse click. Helping a friend do this on his computer I came across a bizarre thing. Having highlighted 5 files in this way, and then let go of the control key and mouse, I was about to click and drag the files, when to my surprise, they replicated themselves as copies on the right hand pane where I was working. I tried repeatedly to carry out the basic operation that I have done thousands of times before, but every time I just ended up copying and pasting more and more files when I did not want to. I have turned the computer off and back on, but still the problem persists. I cannot even select these extra files to delete them without them replicating themselves still further. Any suggestions anyone???