FBI Scam

Unfortunately no Internet Security product can guarantee 100% protection.  New threats for example can only be protected against after they are discovered and updates pushed out to everybody that tell the app how to block such threats.  It's possible if you're doing a virus scan to try and remove the infection that it won't be completely removed.  Malware is desiged to avoid detection and sometimes components can get left behind that trigger a re-infection.  As a worst case scenario it may be necessary to have the PC serviced if the infection keeps coming back.

Antivirus programs are like a good seat belt, it helps and its suggested, but once the damage is done, they do very little.Looks like FBI MoneyPak infection is a rather nasty one and uses a browser security exploit to get through. If this is the infection you have, its pretty tough to get rid of because it infects the master boot record (MBR). You might need a computer repairman. Cox Tech Solutions is one option, but there are others as well. Or if your feeling adventurous and have some experience, you might be able to fallow the instructions given on the bleepingcomputer, but includes booting from a flash drive, which can be difficult. Good luck :-)