bill - 1:30 am on Jun 11, 2013 (gmt 0)
The "call from Microsoft" scam is not relegated just to people who have been infected by something. Often it seems to be a cold call if the media reports are valid.
You were infected for a long time though, so it's possible they have a lot of information about you and you're on a list. I hope that you've taken steps to change passwords and implement multi-factor verification where you can.