Microsoft executives warned Bill Gates to stop sending flirtatious emails to a female employee in 2008, the company has confirmed.
The Wall Street Journal first reported that two senior bosses met with the billionaire after the tech giant discovered inappropriate messages had been sent to a mid-level member of staff.
According to the newspaper, Gates did not deny these exchanges, but said they were a bad idea in hindsight and wouldn't happen again.
The matter was later closed, and no further action was taken because there had not been any physical interaction between Gates and the employee in question.
Microsoft confirmed the newspaper's report to the Associated Press news agency.
In a statement, Gates' private office said: "These claims are false, recycled rumours from sources who have no direct knowledge, and some in cases have significant conflicts of interest."
The 2008 incident came more than 10 years before similar allegations led Microsoft to hire a law firm to investigate a letter from an employee who said she had a sexual relationship with Gates that lasted several years.
The investigation was not publicly known before Bill and Melinda Gates announced they had decided to end their 27-year marriage in May.
Gates, who is worth an estimated $133bn (£96bn), was Microsoft's chief executive until 2000. He stepped back from a day-to-day role with the company in 2008, and departed as chairman in 2014.
It comes as a Microsoft investor calls on fellow shareholders to back a proposal that would force the company to investigate its workplace harassment policies, and release a report about the findings.
Arjuna Capital said: "Reports of Bill Gates' inappropriate relationships and sexual advances towards Microsoft employees have only exacerbated concerns, putting in question the culture set by top leadership, and the board's role in holding those culpable accountable."
Microsoft argues this proposal is unnecessary because the company has already adopted plans to publicly report how it is implementing policies on sexual harassment and gender discrimination.