Why is my computer acting funny?

So I was searching for something and I clicked on a website and something popped up to install but I clicked cancel. Now it's saying I can't enabled my firewall protection for online because it's an unregistered version of windows vista. I've never noticed it before. I don't know what's going on. I'm getting these pop-ups that I need to block this or that from attacking my computer I guess. What is going on? I don't have a virus do I?