My kids computer had that same virus last week. All these porno sites kept popping up and would freeze their computer so you could not access or close anything.
The bogus anti-virus screen kept asking if I wanted to "Protect my computer now". I'm not degreed in computer science but probably know more than the average person and I knew this was B.S.
The first thing I did was to unplug their computer from my network to stop internet access. This made managing things a lot easier because this virus kept regenerating itself.
BTW, it was imported from a media viewer app from MySpace in my case. Kids don't know any better so I didn't raise a big fuss.
I found most of the virus in the "Prefetch" and a couple of other places. Funny thing though, Trend Micro missed it on a scan but my free anti virus software wiped out what I didn't find on the first try.
I think it's good to have backup virus software. I alternate between the two and have very little problems.
If your interested, my free backup virus software came from
http://www.superantispyware.com/P.S. Thanks for giving everybody else a "heads up". I didn't know this virus was so widespread.