I was just called by a gentleman with a strong East Indian accent who said that he was calling from Windows about a series of error messages they were receiving from my computer.  I asked him which computer and he said the one with Windows 7.  I said, which one running Windows 7, please identify it.  He said that all the computers at our house linked to the internet through the same router, so any of them running Windows 7.
I then asked for the name of his company and he said Windows.  I said no, Windows isn't a company, what's the name of your company?  The answer:  Campaign Developers (I think that's what he said), located in Alabama, a licensed support contractor for Microsoft Windows.  I then asked for his name:  Michael George.  I said fine, I'll phone you back, what's your number?  He gave 1-760-283-1718.
I then said, splendid, now what's my name?  He sounded confused, so I explained that if he was getting error messages from my computer and was authorized to do Windows Support, my computer is registered in my name, so he knows my name - so what is my name?
He gave the name under which our phone number is listed in the phone book . . . which isn't my name.  He missed the rather obvious clue that the phone listing is under a male name and I am not a male and don't sound like one.
Terribly sorry, said I, you have made a mistake . . . goodbye . . . then I hung up.
I echo what previous posters have said:  Microsoft does not phone you about computer problems.  Anyone who phones you and claims to be doing so because of something your computer is or isn't doing is a scammer until proven otherwise.