Here is a list of the senior executives including Tony Bates and Terry Myerson who could be contenders to succeed Chief Executive Steve Ballmer, even though outsiders have sparked the most discussion so far.
Satya Nadella: A 21-year Microsoft veteran, he knows the inner workings of the company, especially the hot areas of servers, data centers and online services. Recently promoted to run the newly created 'cloud and enterprise' unit, he controls the infrastructure behind the 'services' side of Microsoft's new vision.
Tony Bates: Came to Microsoft two years ago as CEO of the acquired online chat company Skype, he so impressed his new boss that Ballmer put him in charge of corporate strategy and relations with developers and PC makers.
Julie Larson-Green: A 20-year veteran of Microsoft and acolyte of recently departed Windows chief Steven Sinofsky, she has intimate knowledge of both the Office and Windows units, having led the redesign of both products.
Jeff Raike: As Microsoft approaches a critical transition, his long experience, understanding of Gates' thinking and steady hand might be an effective combination.
Terry Myerson: A young entrepreneur whose web software company was bought by Microsoft in the late 1990s, he might bring a start-up mentality to the top job. Recently selected by Ballmer to run the full range of operating systems - which are still the heart of Microsoft - ranging across Windows PCs, tablets, phones and the Xbox game console.
Eric Rudder: A fixture in the background at Microsoft for two decades, this deeply tech-savvy exec now runs Microsoft's long-term research unit and sets overall technical strategy. He is the nearest the company has to a big thinker in the mold of Bill Gates.
Kevin Turner: Microsoft's Chief Operating Officer for the last eight years, the former Wal-Mart Stores Inc exec is the power behind the company's fearsome sales operation.