...unless you call them first.
A good friend recently received a phone call from "Microsoft support". The caller indicated that they have detected a virus on my friend's computer, and can safely remove it for only $8. The caller almost immediately asked how he would like to pay for it, and mentioned that they accept all major credit cards. The good thing was that you don't have to be a tech savvy to recognize that it's a scam, however, if you receive a call from someone claiming to be from "Microsoft support", hang up unless you called them first and were expecting a call back.