Microsoft is again claiming to be about to drop $300 million on an ad campaign - this time to rescue its flagging Vista brand. The story has been widely reported, although previous "$300 million" campaigns from Microsoft later turned out to be much smaller efforts.

Launches of MSN, Microsoft's search engine, operating system upgrades and other offerings have all won assurances from the Redmond PR offices that they would be supported by massive - in fact $300 million - campaigns.

Measured media reports in subsequent years showed that less than half of the claimed sums had been spent, and sometimes very little at all. In fact, MSN is notable for having had the claim made both in 2002 and in 2005.

Some observers have guessed that the large dissonance between claim and actual delivery could be explained by internal accounting, with sales staffs and promotional efforts that don't pop up in tracked media statistics. Others have guessed that it just makes better news to tell a sometimes gullible trade press that one third of a billion dollars is at stake.

The creative has been developed with Crispin Porter Bogusky, eschewing long-time partner McCann Erickson, who still controls the media buy. The products to push: Vista, Live and things mobile.

This most recent claim involves a campaign centering on creative employing comedian Jerry Seinfeld.