That's what the New York Post is reporting today, citing sources familiar with the situation. If the report about the planned ad campaign is accurate, it would appear to be an extension of the recent Windows Live 2.0 launch, which was seen in part as an effort to refresh Windows with new downloadable applications. And $300 million would be in the realm of what the company has spent on major Windows campaigns in the past.
One quote from the story: "They are trying to make Windows cool, relevant and Internet-centric," said one source close to the company. "They don't want to be seen as a stodgy computer company."