Diane at work just told me she got a call last night from someone (sounding like from India) who said he was from Microsoft, that her PC had a virus, and was broadcasting emails.
He insisted she needed to log onto her PC, and they needed to resolve it right then.

She refused – in the face of repeated insistence that he was from Microsoft, would cancel her Microsoft registration, and her PC would no longer work.

After ending the call, she looked up the number online and found that some people had gone for the scam (the caller is apparently persistent and convincing), and had put in the website/url the caller instructed.Apparently, they convince the user to log on to the url, then drop a virus onto the user’s PC, then want $400 to remove it.
Other users posted that they played along only teasing the caller, or harassed the person calling, and after hanging up, got a subsequent nasty phone call message back from them.

This happened to Diane directly. (The original call, not the nasty follow-up call.) Not a false warning. Forewarned.

-JG

Details from whocallsme.com: http://whocallsme.com/Phone-Number.aspx/9999100102