I had a call from someone claiming to be from Windows Support to tell me that my computer was infected with a virus. Yeah right, except that he knew the CLSID code for one of my windows box's and they are quite different on my two windows 7 machines. To see yours run the assoc command in a cmd box and it will be towards the bottom of the list.
The call was very echo'y, I've been told that's because they use Skype and similar to keep the call costs down.
Plenty of on line mentions of similar scams although I didn't see any reference to them knowing that sort of detail. The Microsoft site makes it very clear that they never cold call regarding virus's.
I think this was the general call that I got.
http://www.scamwatch.gov.au/content/.../itemId/792165
I'm mentioning it here because it was unusual that he could provide what appears to be specific details about my PC. I've reported that to Scamwatch, HP and Microsoft.
Bob