Microsoft is to pay comedian Jerry Seinfeld 10 million dollars to star in a 300-million-dollar advertising campaign for its Windows Vista operating system, according to dpa. The campaign, which is one of the largest ever undertaken by the software giant, is aimed at establishing a cachet for the computer operating system and will feature Seinfeld along with Microsoft chairman Bill Gates. The theme of the campaign will be "Windows not Walls," the Wall Street Journal reported Thursday and will focus on "breaking down barriers that prevent people and ideas from connecting." The campaign is seen as Microsoft's attempt to hit back at Apple's long running series of Mac vs PC ads, which feature a nerdy PC guy losing out to a cool representative of Apple's increasingly popular Macs. Vista was introduced in January 2007 and quickly became the world's dominant operating system since it is pre-installed on the vast majority of new PCs. But it has failed to catch on in the business market and according to a recent article in Computerworld, many PC owners often downgrade their system to run the previous operating system Windows XP, which is considered by many experts to be faster and more stable. Microsoft is currently working on a successor to Vista called Windows 7, which could debut as early as next year.