My computer got hacked?

I know exactly what caused it and the website it came from. After one of my downloads completed, i got hit with a big ad that claimed "antivirus system." After this ad came up, a new icon appeared in my toolbar at the bottom left. now i keep getting slammed with all this stupid crap about "this is infected and this is infected." Anyway. The virus came from www.bekturr.com. I went there and it just says MUSIC ENCODING BLUE YELLOW. So how do I beat this thing? No, I don't have any antivirus stuff anymore. My dad believed that even when it said "expired!" That I was still protected. I tried to tell him.