Hello, Amanda
Welcome you here. Your computer has been locked virus is actually the general name of ransomware, which defines a series of fake warning in name of FBI, United States Cyber Security, here said Depart of Justice and other authorities alike. This ransomware you've mentioned here Your computer has been locked by Department of Justice, Federal Bureau of Investigation virus is, like other ransomware, created by cybercrooks to lock the victim's computer for the sole purpose of money extorting. Other similar ransomware can be listed as Malex ransomware, FBI moneypak virus, etc. By the way, this pc locked virus is also called Americana Dreams ransomware, and you will find the detailed description about it and a related removal guide in another post:
http://forums.anvisoft.com/viewtopic-45-1121-0.htmlTo solve this issue, since the computer infection state seems to leave no choice to unlock that but following steps detailed in the
Option 3 removal of the above stated post on Americana Dreams ransomware.Good luck to you. Any further question in the process, just let us know.