Hi, Twinkling.
In my opinion it would be ever so normal to find porn on your boyfriend's computer. I don't have any hard data, but I am sure that a very large percentage of men with internet access spend at least some of their time looking at porn on the internet. I wouldn't worry about it too much. And as far as getting back at him, unless you genuinely want to look at it, you're not going to get much satisfaction that way. Try asking him if you want to look at it together......I'll bet he's game.