My indescretion was a boot sector virus that would randomly seize control of the computer long enough to beep the theme song to "Cheers". Oh and spread to the boot sector of any disk inseted. To be diabolical it randomly chose to play the song or simply silently reinfect others each time it spread.

They (at my highschool computer lab) were still battling to eradicate it years after I left. I am ashamed. Somewhat.