on 2/25 I received a message that my computer was under attack. A window pops up that appears like the Vista security system that tells me my security measures are too weak and I need to purchase internet security. Having done that, I got a registration code that did not work and immediately realized i fell for a scam. Upon calling the credit card company we found more people on this site who had the same problem.
You can still access your desktop by closing av.exe w/ the task manager. After that, run a system cleaner (search and destroy, and/or ccleaner.) Then, ramp up your internet security. I purchased nod32 antivirus, ran a scan, and it immediately took care of the problem.
My money is still in limbo though, and I had to put a hold (and ultimately cancel) my credit card. If this happened to you - I suggest you cancel your card right away!