Three of Microsoft's top twenty investors are reportedly pressing Bill Gates to leave his position as Chairman, claiming he wields power out of proportion to his actual shareholding at the company he co-founded 38 years ago, and that he might interfere in the selection of Ballmer's successor. In particular, they're worried they'll go with a Ballmer clone rather than someone who can adopt new strategies and bring in substantial changes.

Gates owned 49% of Microsoft before it went public in 1986 but has been lowering his profile at the company ever since he handed the chief executive role to Ballmer in 2000. He gave up his day-to-day work there in 2008 to focus on the foundation. Although still the largest individual shareholder, his stake currently sits at 4.5%, and under a set plan to sell 80 million Microsoft shares each year Gates will have sold his entire holding by 2018.

Microsoft is still one of the world's most valuable technology companies, reporting a net profit of $22 billion on record revenue of $73 billion during its last fiscal year. Under Ballmer's tenure, the company has consolidated 16 businesses that do a billion dollars plus in annual revenue. But its core Windows and Office divisions are under pressure from the decline in personal computers as smartphones and tablets grow more popular.

Another concern from investors is that Microsoft shares have been essentially static for a decade, and many of them accuse the company of being too stingy in rewarding shareholders with dividend payouts.

Microsoft is currently undergoing a transformation into a devices and services company, and though the company's board is backing this strategy, some investors say that a new CEO should not be bound by it.