It seems the Telephone Scam I had reported on before has returned, as reported by a number of clients recently. Please be certain, nobody from Microsoft is going to phone you and tell you that your computer is at risk. The best thing you can do is hang up on them!
It is also the time of year when numerous "electronic greeting cards" arrive in your inbox. You should always be cautious of any attachment and/or web link that sends you to a sketchy website. If you are uncertain about an email, simply delete it and then compose a new message to the person you received it from, asking them if they did in fact send something to you. They can always re-send it. Better to be safe then sorry!