I have a story similar to piecenick's:
I had two friends in college - a guy that I met in my first year and through him his girlfriend. Both were first generation Cuban immigrants, by which I mean both of each of their parents had fled Cuba shortly after the revolution. I knew both for several years and became close friends with each of them, and eventually they got engaged and got married. Up until the marriage, the guy and I shared an apartment and the plan was that when they returned from their honeymoon he was moving out into the new home he and his new wife had just purchased.
The real trick was that the girl's parents were VERY conservative and believed very strongly in 'no sex until marriage' and believed (very wrongly) that their daughter had been saving herself for marriage all along. So...it's the day after the marriage and they are in the airport for their honeymoon trip to Spain when the guy calls me. The problem was that he had several explicit photos and one video of his new wife that demonstrated rather conclusively that she had NOT 'saved herself'. Apparently in all the run-up to the marriage they had completely forgotten about their secret stash, and they had just realized that her mother had planned to come over to our apartment and box up a bunch of their stuff and get it into their new house so it would be ready when they got back from Spain...and they had concluded it was inevitable that she would find their stash and the 'secret' would get out. My buddy asked me if I would do him a HUGE favor and get rid of them before his mother in law showed up, and when I agreed he made me promise I'd destroy them immediately.
Of course I agreed, and he told me where to find the stash; I think it took me all of two minutes after he hung up before I had it in my hands. The girl was every bit as hot as I'd ever imagined and I enjoyed that stash thoroughly for about two weeks while they were in Spain...but eventually my guilt got the better of me and I took the whole pile out to the barbeque pit right before they returned and sent it all up in smoke. Still, I NEVER forgot what I had seen; there was even a funny moment about a week after they were back when the three of us were sitting at their dinner table and she thanked me for taking care of it and then said 'You didn't look at it, did you?' I just chuckled and said to her, 'Well, of course I looked! I couldn't just blindly grab a pile of 'something' and throw it away without knowing I had the right pictures, could I?' She blushed furiously but smiled and agreed with my point, while at the same time he started laughing until he cried. I didn't tell them I had seen the tape, but the point was made that I had seen her in all her glory
So, on point for this thread: Up until the moment I saw those pictures I had steadfastly avoided allowing myself to think of this girl sexually; they were both my friends...but after that point, it was impossible for me to see her without imagining how hot she was and how fun she would be...
There's another story I posted here quite a long time ago...eventually the guy broke off his friendship with me for some pretty ridiculous reasons, and some years after that I ended up hooking up with the girl for a brief time. We talked about those pictures again and I admitted to her then that I had seen the video...and she admitted to me that while she WAS embarrassed she also thought it was incredibly hot that I had seen her naked and wondered if I had ever thought about 'more' with her. Which I did...which is the point of that other story