Steven Sinofsky is stepping down as the head of Microsoft's (MSFT 0.41%) Windows department, and the reason behind it is completely understandable: he just didn't get along well with the executives. But the timing's going to hurt them. In this video, Motley Fool tech analyst Andrew Tonner tells us about the struggles facing Microsoft at the moment as the market shifts away from PCs and toward mobile, and how the company can go forward from here after the loss of a good chief operator.