So my good ol' father was browsing on the internet and, while I'm not sure of the catalyst, there is now a virus on his computer (I think). There is a window that pops up every few minutes that says the computer is at risk, and opening it brings us to Windows security which says there is a threat, clicking that brings us to a web site prompting us to purchase some third party virus protection, which we found suspicious. Additionally opening Windows security normally says there is no threat, and Norton can't seem to find anything either. Does anybody know what's going on or how to fix it?