Which company did Gabe Newell work at before founding Valve Corporation?

Before founding Valve Corporation, Gabe Newell worked at Microsoft. He served as a key member of the Microsoft team, contributing to the development of the Windows operating system, particularly focusing on versions 1.01 and 2.0. However, Gabe Newell left Microsoft in 1996 and co-founded Valve Corporation, which went on to achieve great success in the gaming industry with iconic titles like Half-Life, Counter-Strike, and Dota 2.