Make sure you fully document everything that you have done. Make sure that it's extensive about the work carried out too, as well as your boss' reaction. Also do this NOW, while it is fresh in your mind. You might well need it at a later date for the cops.
Then report this guy, I believe there is a specific place to report child porn nowadays.
Then I would start job-hunting ... I personally would never tolerate working for someone who doesn't seem bothered about finding child porn! There could well be hidden files on there with addresses of little girls & boys this guy wants to meet. It's not something that should be ignored, or taken lightly by your boss. This shows A LOT about his moral standards!
