The best way to handle such browser scams is to kill the browse and any associated child processes using taskmanager. I also never press any “X” or “close” buttons on any browser scam pop-up Windows as you can never be sure what they will actually do. I then shut down the PC and reboot into safe mode where I run a full scan. Sometimes even I use a boot CD and run a scan off it.
As a final step, and the most important thing, I evaluate what web sites I was surfing. Since I’ve had a PC, I’ve only had two instances of such viruses/phishing scam. Others I know were getting such on a frequent basis One friend liked his porn so much he often suffered the virtual equivalent of an STD After some repeated requests for help to fix his PC, which I did, I finally told him he was on his own