Idiots

I spent the day yesterday trying to clean and clear my computer as I found that once again some idiot had inserted himself/herself onto my computer as a user. I found that many of the things I wanted to do would show a pop up window telling me that I just didn't have room left on my pc to that... imagine that. That's when I started looking and found a user in my user list that I had never heard of. Since this has happened once before, I am not a happy camper. That time, I had to have the entire pc overhauled and it cost a bit... We installed a firewall, but it seems that this person is absolutely insistant on using my pc! I also find that I have files that are password protected that I cannot get to even when my anti-virus scans. Ask me if I'm in a bad mood....