In this clip, excerpted from Walt Mossberg and Kara Swisher's interview with Microsoft chairman Bill Gates and CEO Steve Ballmer at the All Things D conference down in Carlsbad, Ballmer explains how Gates hired him during his first year at Stanford business school. Ballmer says Gates called him up and lamented the fact that he "didn't have a twin" he could hire to work at Microsoft. The best part of the tale? Ballmer's voice impersonation of Gates on phone — all squeaky and high-pitched — with his Gatesness sitting right there.