SAN FRANCISCO--Microsoft's operating systems are still vulnerable to attacks, but more often than not it's older versions that are taking the big hits.

That was the message from Scott Charney, corporate vice president in Microsoft's Trustworthy Computing group, when he sat down with me on Tuesday. We chatted about the latest threats, including Conficker. The much-maligned Windows Vista, he noted, wasn't hit in the way that older versions of the operating system were.

"Some of those widesp...