According to a report in Vanity Fair magazine, MicrosoftCo-founder Bill Gates' affair is an "open secret" and everyone around him knows about it.

The report quoted two people familiar with the matter as saying that someone in the small circle of Gates'ex-wife Melinda had worked with private detectives to investigate the matter before their divorce.

A spokeswoman for Melinda Gates responded: "neither Melinda nor anyone under her has ever hired a private investigator."

A former employee of Gates told Vanity Fair magazine that they had seen Gates secretly change cars in the office. Gates sometimes drives a Mercedes to work and leaves an hour later in a golden-brown Porsche brought by his security guards, they say.

"We all thought it was when he was with a woman," the former employee said. I know there are a lot of off-court meetings that are not on his schedule. "

But another source close to Gates told the magazine that disappearing from the office was not like Gates because he was "one of the most stressful people on the planet".

A spokesman for Bill Gates said in a statement in response to the Vanity Fair article: "it is disappointing that there are so many lies about the reasons, circumstances and timing of Bill Gates' divorce. Rumors and guesses are becoming more and more absurd. Unfortunately, people who know little or nothing about the situation are called 'sources'. "