That's a common trick that the bad guys use. The "virus scanner" you saw was probably a virus itself, trying to trick you into panicking and doing whatever it says. The most important thing to do is DON'T PANIC. Don't do anything the "scanner" tells you to do. Close your browser immediately.
If you use comcast they let you use Norton for free. Make it do a full system scan and it will terminate viruses. IF all else fails I think if you just wipe you computer it will be ok. (wipe as in you clear every thing on it and I mean everything.)
spybot.com is great and it's free. Spybot is my goto program when something pops up on mine (not very often). DO NOT pay money to a pop up "virus scanner". It IS a virus....
Malwarebytes.com is great for malware type problems.