Has FBI locked my PC?

Hi there! I`m not a very experienced PC user, but I have some basic knowledge with PCs, however, what happened yesterday with my computer completely freaked me out! I was browsing the net when my PC crashed and I had to reboot it. When Windows finally loaded, a message by FBI stood on top of my desktop and said my PC was locked because of my illegal online actions.

I had no idea what was the problem, but it was obvious that I was unable to use my PC at all and even now I`m still unable to use it. The message is still on my desktop, saying I have to pay a fee of $50 to fix my machine.

I am not sure how to remove this warning, so , please, let me know if you have some idea. I am pretty sure this is some kind of spam or virus, but I don`t want to crash my PC, so let me know a safe way to remove it! Thanks!

 

These links were really helpful that you posted. I also found some more information about the infection http://www.americanpendulum.com/2012/07/11/remove-fbi-moneypak-virus/ and http://botcrawl.com/how-to-remove-the-fbi-moneypak-ransomware-virus-fake-fbi-malware-removal/, but this didn`t help me much. I`m worried I`ll have to format my HDD if I cannot solve the problem, but I really don`t want to do that. I need some simple solution, because I don`t have much experience with computers.