So there is a virus that seems to be more and more common now which basically takes over your computer stating you need to pay money which ranges in price before they will unlock your computer. DO NOT pay! This will not do anything for you other than rid you of some money.

There are instructions out there to manually remove the files / entries for this. If you are not comfortable with computers and/or the registry. DO NOT edit it as you can do more harm than good by editing the registry if you edit the wrong keys.

Just follow the steps here:
linky

Malwarebytes will get rid of this FBI trojan, and this with the other steps will help if you do have other infection issues.