Here's mine - early 90's as well. My rural highschool had three computer labs, one with Macs for doing school newspaper type stuff, one with ancient TRS-80s fo

Here's mine - early 90's as well. My rural highschool had three computer labs, one with Macs for doing school newspaper type stuff, one with ancient TRS-80s for doing programming, and one with ancient PCs for learning typing. The PCs were on a network, and it was set up so you would boot the PC and it would log you into the network server, which would run a batch file from your home directory on the server. Seating was first-come, first serve. So I made a batch file fragment that would copy itself at boot time from autoexec.bat into your profile script, and/or back from your profile script into the local autoexec.bat, to be run by whoever used that machine next. A couple of days later I checked back and it had replicated to every machine in the lab.