It seems only yesterday when Microsoft's position atop the lucrative desktop software market was so unassailable that the FTC had to bust them for monopolistic behavior. Oh wait: it was yesterday. That's why news of Dell and Google agreeing to install Google software on Dell PCs met with a round of gasps heard from Wall Street to Fleet Street.

It's been 10 years since Microsoft first began making deals to pre-install its software on home computers, and the bet was a good one, prompting Microsoft to a seemingly insurmountable lead in the desktop software market. But now Google software will sit in Microsoft's place.

The impact on Microsoft could be stunning. While sales from the "Client" division only make up about 29% of Microsoft's sales as of the most recent quarter's results, those sales represent 63% of the company's operating income. Were the client sales to be impacted only by 10% as a result of this Dell/Google deal, or about 3% of the overall revenue, 7% or more of the operating income would be erased: a serious threat indeed. Fortunes are made or lost on high-single-digit drops in operating income.