I had a similar situation with a "stand over tactic virus", but it was a phone call to my 79 year old Mother, who had no idea that; you just hang up, very quickly ! He asked for her credit card details, and said,"Or I'll destroy your Operating System."
Anyway she did what the guy said, unfortuneatly, except give him her credit card details. The guy totally wiped Windows off of there; I looked with a pclos Live CD, there were some pictures and a few odd files. I believe she allowed the guy to take remote control of the machine through a site.
Anyway I reinstalled XP, but had problems getting the router talking wirelessly to Comp in another room.
In the end got here a new (old - cheap) comp, with Win 7, and being more recent the setting up of Router/Modem in another room to Comp was immediate.
Was a huge scam, the guy rang me weekly for a year before it was finally shut down by Aus. Federal Police about a month ago. Wasn't same guy, obviously, but was based in India, and being a phone call, "This is Microsoft, please go to your computer and do as I instruct you..."
I want that HP Comp, it has a bit of grunt and a big HDD, or I'll pilfer some parts out of it and make one of my other home Computers 'better', lol. With PCLinuxOS installed of course.
The Anti-Virus Software takes at least 25% of the operating power out of the Hardware on all Windows machines I believe, especially as they're getting more bulky and complex. kaspersky; you just about need to do a course to know how to set it these days.