One time, I was helping my friend get a file on his flashdrive.
He had to much space occupied, I had to delete a old folder which only my friend's friend uses, and the file was put in. During deletion, I saw what appeared to be a game of some sort. Curious, I looked up said game on wikipedia. Turns out, my friend's friend had put data for a Adult(If you know what I mean) game on his flashdrive, and he didn't know it.
From that point out, I stopped helping him with such nonsense. I never told him what I saw.