"Hello. I'm a PC. And I've been made into a stereotype," says Sean, right, in the outset of the latest installment in Microsoft's $300 million Windows ad campaign, set to debut tonight in prime time.

(Update, 7:26 p.m.: Watch it here.)

The sixty-second spot -- one of several elements in a campaign that will span print, the Web, television and outdoor -- launches into a series of testimonials by other people, including celebrities and real people, who proclaim, "I'm a PC."

"I'm a PC, and I'm not what you would call hip," says a woman standing in front of a white board. Bill Gates is next. "I'm a PC," says the Microsoft founder, holding a bag (paper) of groceries, "and I wear glasses."

Architect Edouard Francois says he designs green buildings. "Desperate Houswives" star Eva Longoria and husband Tony Parker, guard for the San Antonio Spurs, make an appearance. As does Deepak Chopra, who intones, "I am a PC and I am a human being. Not a human doing. Not a human thinking. A human being."

Update, 9:43 a.m.: The spot closes with the tag line for the campaign: "Windows: Life without Walls." Bill Veghte, senior vice president of Microsoft's online services and Windows business group, said Microsoft felt it had to reclaim the message around its products from Apple and is doing so with the "I'm a PC" ad, which will start in heavy rotation on U.S. television tonight. Shorter versions will appear across the Internet as part of a "very significant" online buy.

"We need to be out telling our story to our customers," Veghte said. "These are Windows customers telling the story of what Windows represents. ...

"Windows is about all sizes and shapes of different PCs and devices and software applications, and so to the extent that Windows is inclusive, that is something we want to make sure people understand. It's not a stereotype. It's an inclusive set of experiences that celebrate and support diversity and individuality and choice."

Starting this afternoon on Windows.com, people will be able to upload their own "I'm a PC" testimonials, which will be incorporated into other parts of the campaign, including a video billboard in Times Square in New York City.

"The whole approach is very dynamic and viral," Veghte said. "... The celebrities we use today will certainly evolve as we go forward."

Comedian Jerry Seinfeld does not appear in this part of the campaign. Eric Hollreiser, a company spokesman, said "that doesn't mean you won't see him in the future."

There was some speculation yesterday that the perplexing Seinfeld ads were pulled because of unfavorable response. Regardless of how they were received, they managed to build tremendous buzz around the campaign. And Microsoft said from the outset that it planned the Seinfeld ads as an introduction -- given that it has not done much mass market consumer advertising since the launch of Windows Vista in early 2007 -- to be followed by more concrete messaging.

(You also won't see Seinfeld at today's Microsoft company meeting, which begins at 11 a.m. at Safeco Field -- and is closed to the public. Microsoft tapped Rainn Wilson of "The Office" to emcee the annual event, which Bill Gates will not attend for the first time in recent memory.)

To hammer home the "Life without Walls" tag line, Microsoft also launched a flurry of print ads featuring a Windows "Manifesto," which Veghte described as a document used internally "quite a bit." (It appeared in a two-page spread in the A section of The Seattle Times.) It carries the heading "Windows VS Walls" -- a not-so-veiled reference to the closed system of Apple, which makes hardware and operating system software.

The manifesto, printed next to a picture of a guy who has just cut a Windows-logo-shaped window through the wall of a house with a sawzall, reads:

"This epic struggle explains why we make what we make and do what we do. The thing that gets us out of bed every day is the prospect of creating pathways above, below, around and through walls. To start a dialogue between hundreds of devices, billions of people and a world of ideas.

To lift up the smallest of us. And catapult the most audacious of us. But, most importantly, to connect all of us to the four corners of our own digital lives and to each other. To go on doing the little stuff, the big stuff, the crazy stuff and that ridiculously necessary stuff. On our own or together.

This is more than software we're talking about. It's an approach to life. An approach dedicated to engineering the absence of anything that might stand in the way ... of life.

Today, more than one billion people worldwide have Windows. Which is just another way of saying we have each other."

Other print ads will highlight Windows across a range of outlets, from the PC, to mobile devices to the Web.

Stuart Elliott, advertising writer for The New York Times, has an interesting piece analyzing the success of the Windows campaign so far and the risks and rewards of countering a rival's attacks.

What do you think of this next installment in the campaign?