Sean Siler, IPv6 Program Manager at Microsoft, is leaving the software company, reports Seattlepi.com. Who? Sean Siler, that's who! He's the guy who starred in some of Microsoft's "I'm a PC" commercials, which were obviously created in response to Apple's anti-Microsoft "Get a Mac" advertising campaigns. Sorry, Apple fanatics, he'll still be a PC and has mucho love for the Redmond software giant.