Microsoft Corp., the world's biggest software maker, said that Seamus Blackley, co-inventor of the Xbox video-game console, is leaving the company four days after it slashed its sales targets for the device.
Blackley, who helped persuade Chairman Bill Gates to build the money-losing Xbox, plans to form a new gaming venture.
James Bernard, a spokesman for the Redmond, Wash., company, declined to say who would assume Blackley's responsibilities.
Microsoft, which for years shunned selling products other than its flagship personal-computer software, introduced the Xbox in the U.S. in November.
Sales have tapered since then and have trailed forecasts in Europe and Japan, forcing the software maker to reduce sales estimates.