I cracked all the passwords in my MS-DOS based computer programming class by modifying the boot floppy. It was pointless since the assignments were easy and I had perfect grades in that class, and the only thing this allowed me to do was steal other peoples' homework. But eh, boredom....

I also figured out how to auto-crawl the networks of all the schools in our district, which, as a self 15 year old whose only experience was non-networked DOS, is still a proud accomplishment. The only things I found were a bunch of printer management, some office form templates, and a cool video game that was like sim-moonbase.

But then my teacher found the file in my home dir called passwords.txt, and I was busted. Oh well. Instead of an FBI file, I got a detention, and I had to teach him how to write-protect the boot floppies so no one else could do what I had. (he didn't need to know that you could reverse the write-protection with a piece of electrical tape)