Microsoft CEO Steve Ballmer has faced his first public call to step down, as hedge fund manager David Einhorn accuses him of being "stuck in the past".
Speaking at the annual Ira Sohn Investment Research Conference in New York on Wednesday, Einhorn claimed that it was time for Ballmer to step down and "give someone else a chance".
"His continued presence is the biggest overhang on Microsoft's stock," he said, according to a Reuters report.
Einhorn's Greenlight Capital hedge fund currently holds around 9 million shares in Microsoft, 0.11 per cent of the company's outstanding shares.
The comments came as IBM overtook Microsoft in market value for the first time in 15 years, as Microsoft's shares continued to remain static - despite a small boost following Einhorn's comments.
Apple passed Microsoft as the biggest tech company in the US in 2010, a position Microsoft had enjoyed for most of the last decade under Bill Gates' leadership.