Look out for this AntiVirus redirect - it\'s doing the rounds. (including the News of the World Website)
 

Just had this happen to my Mac. Clearly it wasn't the real thing since I don't run vista, I'm running OS X.
http://i37.tinypic.com/33fdrnk.png
It's not a virus so many anti-virus programs won't pick it up. It is just spyware in it's worse form.

It's doesn't mean there is anything on your computer, it's just a load of fake images making it look like it's scanning your machine. Basically it is just an advert so it can infect your system with loads of rubbish.

It tries to install a program onto you computer, which will then keep telling you have a virus until you buy there software which just uninstalls the program it installed in the first place.

Update - I wasn't sure what site I got this from but I can now confirm it came from the News of the World website.

I got something like this on my mac, good thing about this being on the mac is that i could tell it was weird because i dont have vista ha. But anything like a virus check like this you should ignore straight away, the way people fall for it is not only the officialness about it but the way you try and close it and it keeps saying "Are you sure" so annoying it can take a while to close it but make sure you do :)