ROFL must use a few of those on school computers
BTW if you're on a network the DOS command net send ... is really funny as well.
-First you can just send single messages to computer-illiterate people. We were sending msgs like 'This computer shouldn't be used for homework. Fatal error! Please reboot' and those girls on the computer were like WTF, what is happening. Unfortunately we were laughung so hard they noticed.
-Now everyone gets used to the command. Great! Create a batch file which keeps on sending, or better use 3 files to spam the same computer
-Finally you can use net send with the network name to spam all the computers at the same time (much fun coupled with batch files
)
Alternative fun, try to find an someone who doesn't care about getting kicked out and let him search the librarian's computer (schools network has ...(number) so he tried the numbers) with abusive messages