PC problem
 

My mother opened one of her emails and got a pop-up called "Personal Antivirus", and she clicked on it thus installing it. What I want to know is what immidate danger does it cause and is there a safe way to remove it without reinstalling windows as a whole because it says there are over 100 virus' and you need to pay them to remove them yet I ran the anti-virus and anti-spyware from rogers and it said the computer was clean. I'd try google but it's really slow right now.