This story isn't necessarily my fault so much as it is my brother's, but it really forgeted my system up so bad because he's a loving dumbass. I was like maybe 10 at the time, I wasn't too good with computers yet and I didn't really know how to just back up my files and reinstall Windows.
When I was young I tended to just leave my computer on 24/7, because there was no real need and it was very quiet anyway. I didn't even lock the computer, I didn't really have anything to hide and I trusted that no one would do stupid stuff with my computer.
One day I come home from school and see my brother on my computer. Very unusual because he didn't even need to use my computer, he had his own computer (and better too). Turns out he was using my computer as a dummy computer for some stuffty World of Warcraft hack that he was trying to check to see if it was clean. I was pretty pissed off at this because god knows what loving sketchy Siberian forgeter wrote this stuff (thank god I didn't do anything important on my computer, i.e. personal files/photos of myself/etc. traceable items), but my brother kept reassuring me that he cleaned all traces of the stuffty hack on my system. Meanwhile my brother is like typing some stuffty reply to whatever hacker he was PMing on some sketchy-ass WoW forum about how "he used his sophisticated backup servers to find out that the hack was a dud", loving stuffhead. I said whatever, and then turned off my computer because I had ended up getting grounded that day for a bad grade. My punishments tended to last pretty long, even for things such as getting a C on a report card, so I ended up having to wait like around 3 months til the next report card to use my computer again. I eventually forgot about the whole ordeal, and I turned on my computer when I got ungrounded.
So I turn on the computer and lo and behold there are like loving pop-ups left and right. My entire 1024x768 screen is literally full of pop-ups and my system is probably on the floor crawling like a sloth trying to keep up (it was a Pentium 4 with like 1GB of RAM, so this was not fun). Meanwhile, at least 3-4 audio advertisements are playing simultaneously. There is literally no hope for this thing. Because I had no clue what the forget to do, I went to my dad (who's very much knowledgeable about software and some hardware, and the whole reason for me being into computers) for help. He went out and bought this Pandasoft Anti-Malware complete security thing. He went into safe mode, I'm assuming, and completely swiped away all 500+ adware/spyware programs. Yep. One single stuffty WoW hack gave me over 500 malware programs.
This wasn't the end though. Every time the Pandasoft software would block a pop-up, attack, whatever it was, it would make that typical "pop-up blocked" sound from Internet Explorer, and minimize whatever game I had going. Which was really loving annoying. Then eventually I got smart enough to reinstall Windows and did it.