I had this yesterday, only mine was Metropolitan Police, demanding £100 to unlock. ( I have Windows 7 Ultimate.) Following a Google suggestion, I restarted while pressing F8 repeatedly, and this worked and I was able to start in Safe Mode with Networking. This seemed ok, and following the Windows Help suggestions, I was able to take programmes back by 3 days using Windows Restore. I found Norton had been turned off, and restored this using Norton's "FIX", and then ran a full system scan which found only tracking cookies. I am hoping; that everything is now ok - all online bank/card accounts are ok so far and it is now 24 hours since the incident. I am also hoping that Norton have an update in hand which will stop this virus