FOR a company whose most visible employee is a softly- spoken geek fond of words such as “super” and “neat”, it’s unusual to hear of senior Microsoft executives launching into foul-mouthed tirades.

But that is exactly what Steve Ballmer, Microsoft’s chief executive and close friend of Bill Gates, its co-founder, is alleged to have done, according to a court filing by Google, the internet search company that has overtaken Linux as Microsoft’s new biggest enemy.

Mr Ballmer, who is hardly a retiring individual, is said to have threatened to “f***ing kill” Google and “f***ing bury” Eric Schmidt, Google’s chief executive, after hearing that Mark Lucovsky, a senior Microsoft engineer, was leaving to join Google in November last year. Mr Ballmer is reported to have at the same time thrown a chair across the room.

For all its public posturing as your friendly technology Goliath, Microsoft is, as Mr Gates would say, “super-competitive”. It is not easily frightened.

But fear is the only thing that could prompt such an outburst of anger and bitterness from Mr Ballmer, and that fear is rooted in the knowledge that Google has the potential to do Microsoft untold damage in markets it has long dominated.

Kai-Fu Lee, another senior Microsoft employee who quit the Seattle firm to join Google, is the personification of that very real threat. Lawyers for Microsoft say Mr Lee e-mailed Google stating: “I am currently the corporate vice-president at Microsoft working on areas very related to Google.”

“He was saying ‘Look what I did at Microsoft — and look what I can do for you’,” said Jeff Johnson, Microsoft’s lawyer.

Having swiftly overtaken Microsoft in the internet search market, Google has moved into new markets such as internet telephony, instant messaging, free e-mail and desktop software. This is no longer a quirky, little internet start-up.

Google is hardly the David in this battle, with a valuation of more than £40 billion.

There is now a strong expectation on Microsoft’s campus at Redmond, near Seattle, that Google is building an internet browser that would do battle with Microsoft’s Internet Explorer.

Mr Gates has acknowledged the similarities between his own company and Google. Earlier this year he told an interviewer that Google was “more like us than anyone else we have ever competed with”.