When I was 5 and i dint know about viruses, I would download random crap like those cursor programs and bombard the PC with junk.
Our PC got the desktop background replaced with a dark blue background full of 0s and 1s and in red text "WARNING: Your PC is infected" or some crap along with other info, and I couldn't open any programs, and the malware tried to make me put in credit card info and some other crap.
If anyone finds the wallpaper the malware used online somewhere, I'll give you a cookie for bringing me nostalgia. :^)