Seamus Blackley, the co-creator of Microsoft's X-Box, has resigned to launch his own games venture.
The move comes less than a week after the company said sales for the video game system were slower than expected.
Last week, Microsoft said that by the end of June it expects to have shipped 3.5 million to 4 million X-Box consoles worldwide, down from an earlier estimate of 4.5 million to 6 million.
Blackley, who said he and a group of business partners plan to launch a new Seattle-based game industry start-up in two weeks, insists his resignation is not related to X-Box's sluggish sales.
Echoing company officials who said he had essentially finished the job he set out to do by developing the X-Box hardware, he commented: "There's no good time to resign, but nobody in the industry is surprised by this.
"I've really poured my entire soul into X-Box," Blackley said. "There's no way I would leave if there was something wrong."
Blackley joined Microsoft in 1998, initially working on Windows, before he and a group of colleagues dreamed up X-Box in 1999.
Microsoft launched the game machine in November, touting it as a first step toward a broad vision of an interconnected living room, powered by Microsoft software and hardware ranging from set-top boxes to digital music and video players.