how could you fall for that?
Never, ever, pay when your computer demands money. No legitimate buisiness/agency does that.
As far as im aware, the fbi arent into extortion

Unfortunately, this is a scam that has been going around for years and people still seem to follow it. Part of it is probably because of how legitimate it looks. I mean look at it, it has a government seal, law citations, and everything! The sad thing is, you can't use your computer to look up if any of this is all true anyways.

This warning plays off of the SOPA scare that happened a while back, but it's really a virus, which means you had to have been doing something stupid to get it. Either way, it locks your computer and holds it "ransom" until you give some guys $200. Creative, isn't it? It makes you pay through "Moneypak" so it seems even more legitimate. Furthermore, it tells your it will erase all your computer data if no action is taken in 72 hours, adding a sense of urgency to the warning.

While I'm not sure about the data erasing thing, it should be pretty obvious that the rest of the letter is a bluff. If you do get the virus, here's how you can remove it (quoted from http://guides.yoosecurity.com/how-to-unlock-pc-from-stop-online-piracy-automatic-protection-system-malware/ )

Step A: Reboot your infected computer and keep pressing F8 key on your keyboard. Use the arrow keys to highlight “Safe Mode with Networking” and press E/Enter.

Step B: Press Ctrl+Alt+Del keys together to open Windows Task Manager and then end related process [Stop Online Piracy Automatic Protection System].

Step C: Open Control Panel from Start menu and go to Folder Options. Under View tab to tick Show hidden files and folders and non-tick Hide protected operating system files (Recommended) and then click OK.

Step D: Press Windows+R keys to open the Run window and then type in regedit to open Registry Editor.

Step E: Find out and delete all these associating files and registry entries as below:

Go to %userprofile%appdatalocaltemp

The virus can have names other than “random.exe” but it should look like it doesn’t belong and should have a create date/time the same as a .class file if you sort by file mod/create time you’ll find it.

%AppData%[rnd].exe
%Documents and Settings%[UserName]Application Data[rnd].exe
%AllUsersProfile%Application Data.dll
%AllUsersProfile%Application Data.exe(rnd)

HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun “[rnd].exe”
HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionSettings “net
HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun “[rnd].exe”
HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionWinlogon”Shell” = “[rnd].exe”

Yeah this is fake, sopa failed to get passed and if it was legit than it would still activate in safe mode.

It has always amazed me how people can actually fall for this stuff. But then again there are a lot of people who will put their personal details into anything that asks them to. The kind of people that trust anything they find on the internet.