I don't know. I have windows security essential installed and running. Using IE9. Yet I browsed to a web site via google that had the picture of a flower. Next thing I know "win 7 antivirus 2011" has taken over my PC.  Could not open new tabs in IE9. It replaced ms security essentials. I am running as a user account.  how does it do what it did?  I got rid of it by killing a few processes.  But I have not rebooted since, so probably it is going to start running again. I have Java on the PC and I think I saw something about Java when I clicked on the images in IE9.  I can certainly see why people don't want to run Windows if your PC can be hijacked like that.