Microsoft on Thursday will unveil the second phase of a $300 million ad campaign that's designed to burnish the somewhat staid image of its core Windows OS franchise.

The latest ad, a 60-second spot called "Pride," aims to challenge the notion, instilled by Apple's highly successful "Get A Mac" advertisements, that Windows users tend to be dull, middle-management, bean-counter types.

"I'm a PC, and I've been made into a stereotype," says an actor who mimics Apple "PC Guy" John Hodgeman, in the new ad's opening sequence. The actor, in fact, is a Microsoft computer engineer named Sean Siler. Hodgeman's portrayal of an anthropomorphized, and highly put upon, Windows PC helped make the "Get A Mac" campaign a TV and Internet smash.

Microsoft's new ad continues with an eclectic group of individuals from various walks of life -- musicians, researchers, farmers, merchants, and even Bill Gates himself -- testifying that "I'm a PC." It's set to debut during Thursday evening's broadcast of The Office on NBC.

"The goal is to celebrate the basic truth about Windows, which is that it's used by nearly a billion people around the world," said David Webster, Microsoft's general manager for brand marketing, in an interview Thursday. "And that those people do an amazingly diverse and interesting set of things with it."

The ad comes on the heels of a pair of spots in which Gates and comedian Jerry Seinfeld, both multimillionaires, roamed the country trying to connect with everyday Americans -- a sign that Microsoft may have conceded that its software development process has become too detached from the wants and needs of typical computer users.

Windows Vista, which debuted last year, was widely criticized for having numerous extraneous features that weren't likely to be used much but which require a considerable hardware footprint to run properly. Partly as a result, Microsoft in recent months has been losing market share to Apple, whose Leopard OS is viewed by some critics as slicker and more elegant than Vista.

The Seinfeld ads, however, left many viewers and advertising experts nonplussed. The spots did not mention Vista, or even Windows, and many commentators thought they weren't very funny, despite Seinfeld's presence. "Whether or not people get all the details of a narrative is a fair question," said Webster.

Microsoft has discontinued the Seinfeld spots, but not as a result of the critical reaction, according to Webster. "The whole plan was for the Seinfeld ads to be a lead-in," said Webster, who added that their brief, two-week run "is about average for a teaser campaign." Seinfeld was reportedly paid $10 million for the work, though Webster said that number "is not entirely accurate."

Whether the new ad will be greeted more positively is an open question. Like the Seinfeld spots, it does not mention Vista or Windows. Webster says that's by design. The overall campaign will include print and online segments that will specifically feature Windows Vista, while the television ads are designed "to take back the PC brand," said Webster.