Probably a crapload of temp files. I hate Windows.
But your story reminds me of my college days, when computers took up the space of a small room. You operated them with dumb terminals. One wiseacre inserted a program which would halt your program run and display on your terminal screen:
"I WANT A COOKIE!"
It stumped the powers that be for awhile until someone figured out if you typed the word COOKIE, the computer would then display "UMMMMM! (BURP)" and then resume running the program it halted.
Cute, but the person or persons responsible would have been hung in the college quad if they tried that during exam week.