sounds like he just went on one of those warez websites that had a routine javascript pop-up that simply said "Hey you got sum viruzez! Why not download these trojans to scan your computer forever and ever?" It's a 80% certainty that there was never any virus involved, just an irritating message that misinformed him. There's loads out there, designed to make the web illiterate feel like "shit I gotz viruz!" Why all they are really doing is pulling you into one of their virus scanner purchase schemes.
My advice, if you DO NOT browse porn, DO NOT search for keygens, warez, porn, if you DO NOT open every email you receive and can instantly tell that "omg this person wants me to give them all of my bank details and/or porn". - Then for 99% of your internet browsing experience you will not need an antivirus scanner. All you will need is Spybot running in the background so you don't look like a peenus when you tell everyone "I got no virus scanner". The world has been sold the idea of internet security by fucktards like Norton who make a lot of money out of the sheeple who likes internet porn.