Sometimes I am online and I notice that a website keep replicating itself over and over, each time I click out of the web pages they seem to be opening even more, I normally have to shut down my computer to get rid of it.

Not necessarily a virus, but perhaps a problem with some kind of spyware or a browser hijacker. You should look into utilities that will deal with these kind of problems.

Thanks for the response. I asked this question on a different thread and I seem to get it more and more since the service pack 3 update. I'll see if there's something out there to stop it happening now I know what I'm looking for.