The FBI scam virus in essence locks your computer on a scam screen stating you broke some law about pornography (not that ANYONE on this site would watch porn on their computers) or bestiality or whatever. You could also go to jail etc., BUT pay a $200 or $300 with a moneypack card in 72 hours - all will be forgiven and your computer will be unlocked. This is what is referred to a "ransom ware" . OF course it's BS. However it is one of the more common virus out there today. There are at least a half dozen threads on this site about variations of the virus.
OK - I caught this bad boy the other day and it was tricky to fix. There are thousands of threads and commercial sites that propose to fix this. Here's the problem. If you only have the one account set up on your computer, you can't even get on the internet. And even if you have another account on your computer, the frozen one is probably your main account with administrative rights, which you are going to need. You can't even access the frozen account by starting in the safe mode because the latest version of the virus reboots your computer. I'm going to give simple instructions on how to beat this thing.
*turn off your computer
*turn on your computer while tapping F8
* a black & white screen will come up with various options that you can arrow to. Arrow to the option "Safe Mode with Command Prompt.
*Your normal choice of accounts will come up. Log on the main one as you would always do and you will get a command prompt like this: WINDOWS/System32/. Type w/o the quotes "control.exe".
*The control panel will come up in a goffey font - navigate to user accounts.
* set up a new user account - call anything you want, but give it administrator rights NOT standard.
* shut down your computer and then restart it normally. Open your new account, go to the internet to this addy: http://www.surfright.nl/en/products/ and download hitmanPro. Make sure you get the correct one - there's a 32 and 64 bit version. Do not download before you need it - they only give you a 30 day free trial. Then go here and download the free version of Malwarebytes: http://www.malwarebytes.org/lp/malware_lp_form/ and update it as needed.
*restart your computer tapping F8 until the B&W screen comes up. Arrow down to safe mode with networking and hit enter. Sign in to your new account and run hitman. When that finishes and you let it clean up what it found run a full scan (not a quick scan) with Malwarebytes - this could take hours. Clean anything it finds.
* restart your computer and sign into your regular account. Should be just fine.
Hopefully I saved someone the hours of agony these bastards cost me. Of course for good reason - I would never let a computer store or a remote geek have access to my computer, so I had to do it.