One: Can you put that file into a password-protected file and send it to a good friend to keep? Then delete it off your computer so you're not tempted all the time. I understand the temptation to look at that stuff is irresistible while it's on your computer.
Two: If you had a dvd of a REALLY, REALLY bad movie - (like Gigli? lol) - would you keep watching it? Over and over? Of course not. So you need to stop watching this bad movie over and over in your mind. When you find your thoughts drifting to those chats, visualize a big red STOP sign. Sounds silly, but it does work!