'I'm a PC' made on a Mac

Microsoft's "I'm a PC" advertising campaign was created on a Mac and the celebrity spruikers brought in by the software giant are all professed Apple fans, it has been revealed.

Hidden information contained in images from the ads published on Microsoft's website show they were created on Macs, a Flickr user revealed in a published screen shot.

Microsoft responded by quickly scrubbing the hidden "metadata" information from the images.

It issued a statement saying: "As is common in almost all campaign workflow, agencies and production houses use a wide variety of software and hardware to create, edit and distribute content, including both Macs and PCs."

The revelation is ironic because the ads are part of a broader $300 million campaign designed to spruce up Windows Vista's image and tout the PC's advantages over the Mac.

Microsoft has already run two ad spots featuring Microsoft founder Bill Gates and Jerry Seinfeld awkwardly meeting in a discount shoe shop and attempting to reconnect with real people by moving in with a normal family.

But even though a third ad featuring Seinfeld was filmed, Microsoft dumped the comic last week in favour of new ads featuring more current celebrities such as actress Eva Longoria, singer Pharrell Williams and even author Deepak Chopra declaring "I'm a PC".

But all three are Mac fans, Silicon Valley gossip blog Valleywag revealed. Longoria owns a MacBook and Williams carries an iPhone encased in gold, while Chopra, in a column on nuclear weapons published in the Huffington Post, said it was "good to sell more iPods" as they were "entertaining and harmless".

Seinfeld used a Mac in the apartment he lived in on his namesake show and has even appeared in an old Apple "think different" ad.

The Seinfeld ads didn't mention Microsoft's products but now the focus has shifted to Windows Vista in a second wave of the campaign dubbed "I'm a PC".

The new ads are a direct attack on Apple's "I'm a Mac, I'm a PC" ads, which portray the Mac as cool and intuitive and the PC as boring and clunky.

Microsoft has ignored Apple's ads at its peril, allowing the Mac maker to own the narrative and frame the PC's image. Now the company is looking to use Apple's stereotype to its advantage.

The ads will seek to counter Apple's elitist Mac user vibe by including a slew of everyday PC users, such as scientists and teachers, espousing the virtues of their platform of choice. In one spot a diver appears in a cage surrounded by sharks holding up a sign saying "I'm a PC".

Microsoft is encouraging people to "tell us what kind of PC you are" by submitting their own videos to its website centring on the "I'm a PC" theme.

The company will choose some to display on the big screen in New York's Times Square and in its online advertising.