Some time around 2010 or so I found a FREE DOWNLOAD for some software I wanted on Youtube. Normally I wouldn't fall for such a thing, but the video had a huge amount of likes and a basically no dislikes so I thought it was legit (I wasn't well-acquainted with the concept of view bots). Ended up with some nasty malware, had to reinstall. Don't run executables off youtube, kids.
Also there was a point before that I got ultra-paranoid about my computer having a virus, and I would Google processes in task manager and got super scared and installed some fake rogue antivirus from a 'company' called Uniblue. A lot of their 'marketing' was pretending they were part of Microsoft, and I thought it was super legit. It wasn't. Turns out being paranoid about computer security when you are completely computer illiterate is a perfect way to get malware.