Microsoft started a $300 million marketing campaign on Thursday, aimed at improving the image of its Windows Vista operating system and strike back at Apple's "Mac vs. PC" ads.

The first commercial of Microsoft's new marketing push aired on Thursday.

Despite selling more than 180 million licenses since its launch in 2007, Windows Vista continues to suffer from the perception that the operating system is clunky and hard to use compared with Apple computers.

That image has been stoked by Apple's "Mac vs. PC" ads featuring a geeky and unfashionable PC guy unable to keep up with a better-looking, hip Mac counterpart.

Apple has steadily gained market share against PCs in recent quarters. In the June quarter, Gartner said Apple accounted for 8.5 percent of U.S. computer shipments, a rise of 38 percent from a year earlier. That outpaced the overall U.S. computer market growth of 4.2 percent.

Microsoft said the commercial is part of a broader, long-term initiative to change consumers' perception of Windows, which will include setting up a retail corner at several hundred Best Buy and Circuit City stores staffed by "Windows Gurus" to explain the benefits of Windows.

The company also said it has been working with PC makers to optimize systems to speed up computer boot times and improve the overall experience of using a Windows machine.

All the major PC brands are expected to introduce new or revamped models, which Microsoft calls a new category of PCs, with improved designs in the next few months.