FBI money pak please help

Hi,

I got the FBI needs a $200 wallmart gift card lock down screen 2 nights ago on my Vista home HP pc. I went into safe mode and scaned with Norton got nothing. did a system restore and now my pc seems ok, however, I downloaded the update  for norton internet security and now it tells me that I am "At Risk" and I am "not protected by SONAR Advanced Protection" it will not fix itself. I think my PC may still be compramised.

Please help,

Thanks