The campaign to back MSN 8 will kick off with a celebrity event in New York's Times Square with Microsoft chairman Bill Gates and retro rocker Lenny Kravitz on October 24. At the launch Kravitz will perform his hit single "Fly Away", which features in the campaign.
The "it's better with the butterfly" campaign, which runs through mid-2003, is the largest ever for MSN and is double the amount previously spent.
The global campaign will see online, print, radio and television advertising aimed at selling the upgrades Microsoft has made to its online subscription service, which, as well as accessing the internet and e-mail, will protect PCs from viruses and handle digital photos.
Yusuf Mehdi, vice president for MSN, said: "We are investing $300m to communicate with people about MSN 8 because we want consumers to know that finally there is a better alternative to the status quo when it comes to internet services."
The launch comes at a time when rival AOL is suffering from a harsh fall in advertising revenues and failing to encourage enough users to move to its high-speed broadband service, which promises higher revenues.
The campaign for MSN 8 will break simultaneously in the US and Canada before rolling out to Europe and the rest of the world. Microsoft said that total monthly subscriptions for its MSN service reached 9m in September.
Bob Visse, director of MSN marketing at Microsoft, said: "MSN 8 gives consumers a reason to be enthusiastic about the promise of the internet. Now people can expect less unwanted e-mail, more effective parental controls and a better overall browsing experience."
The ads were directed by Phil Joanou, who among other things directed the sitcom "3rd Rock from the Sun", and have been created by McCann-Erickson/San Francisco.
The light-hearted ads show the butterfly characters helping consumers reduce the flow of spam and more easily get involved in the online lives of their children. Other ads highlight additional features built into MSN 8 to address the desire of consumers to communicate more easily with friends and family via instant messaging, and create vibrant e-mail messages with photos and other personalised touches.
The above the line campaign will be supported by Microsoft's largest-ever online ad push. The five-day online blitz for MSN 8, developed by interactive advertising agency Avenue A Inc, is designed to reach more than 90% of the available and active internet audience.
In addition to the advertising campaign, other marketing activities will include direct mail.
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