Help! I have a fake windows security center virus?

Let me start off by saying what actually happens with videos. Whenever a page comes up that has a potential video on it, ones in which you can click a play button, my computer freezes up immediately. I ran a virus scan and there are no viruses. Literally, a second after the page comes up it freezes and the "program is not responding". It was working fine early today. Now that I think back though, a message came up that was asking for me to grant permission or something and I may have clicked never but I can't remember what is was asking for etc. Are there any common downloads I could do or any security options that I can get around? iphone unlock