Hah! Exact same thing, I used... Borland Basic, IIRC, to build the executable that I called from autorun.
I collected many passwords - I never used them or intended to, I just wanted to see if I could do it.
I made the classic mistake though - I told someone about it. A few days later word got around. I was suspended for a week and was banned from computers for the rest of my time there.
Edit: Now that I think about it (I haven't in years): What kind of response is that? Someone shows some creative thinking and does so in a way that is obviously[1] quite naive/without ill intent. While I understand that you want to discourage the specific behavior, perhaps steering the culprit to use talents with more foresight would have been a better answer.
[1] Looking back, I was something of an asshat in the personal skills department so it's entirely possible that they simply didn't believe my lack of nefarious intent.
Actually, I doubt it had anything to do with your personality (and if it did, shame on the authority figures - and the same is true if they were reacting to being made look foolish). No, instead I imagine this was a pure security play: you had a bunch of passwords, and you hadn't done anything with them yet. But they would have had to believe that (and chances are they had no way to independently verify this) and in addition that you would never do anything with them in the future. The second claim is rather tougher to believe than the first.
So in the simplest possible manner you became a "known threat", and they dealt with you in the simplest possible manner, digital ostracism.
Now we can all tell the alternative story, about the wise teacher who sees something special about us in the misdeed, and who takes the time and the risk to cultivate that positive seed rather than throw the baby out with the bathwater, so to speak. Our very own Mr. Miyagi to safe us from a misspent youth, and who understands our behavior as an expression of exploration ignoring limits, outsmarting the system, rather than your basic mean-spirited destruction for no reason. (Although tagging and hacking do share many qualities, and both are driven, I think, by a young man's desire to prove himself, and yes, even aggrandize himself as someone special - bold, clever, crafty, and someone who can't be "kept down by the man". Rebellious, but also desperately needing to prove himself.)
(Of course in this story the Mr. Miyagi would have hacked onto your personal systems, encrypted the passwords you'd stored, and then left a personal message notifying you that if you wish to understand what he did and how he did it, he'll meet you after school in room 10 for a primer on real hacking.)
I collected many passwords - I never used them or intended to, I just wanted to see if I could do it.
I made the classic mistake though - I told someone about it. A few days later word got around. I was suspended for a week and was banned from computers for the rest of my time there.
Edit: Now that I think about it (I haven't in years): What kind of response is that? Someone shows some creative thinking and does so in a way that is obviously[1] quite naive/without ill intent. While I understand that you want to discourage the specific behavior, perhaps steering the culprit to use talents with more foresight would have been a better answer.
[1] Looking back, I was something of an asshat in the personal skills department so it's entirely possible that they simply didn't believe my lack of nefarious intent.