Ever wanted to send someone a disk to make it so they would get "owned" upon bootup?
step1) Take a 3.5in DOS boot disk and make a BAT file on it called autoexec.bat (if it has one already, edit it).
step2) Put this line in the autoexec.bat file
step3) Put your own label on the disk. Maybe "Duke Nukem, this
commercial game requires you to boot from the disk for copy protection"
would be a good idea.
step4) Give it to someone, or just set it out on the sidewalk and hope someone thinks "Wow! Cool! I always wanted it".
Result) When he/she boots from that disk, it won't start any game.
Eventually the victim will give up, think the disk was just broken and
throw it out. Next time they start their computer, it won't boot, but
instead will either show a black screen or an error message. A computer
can't boot without command.com, you see.