For some reason, Microsoft hasn't been able to replicate its desktop dominance on mobile devices. The company first released Windows Mobile in 2000 for cellphones and pocket PCs, and while later versions captured a significant portion of the mobile OS market, the platform never really caught on. Microsoft's second attempt at a mobile OS -- Windows Phone -- arrived in 2010. While it improved the experience of Windows Mobile, it also struggled in the face of Apple's iOS and Google's Android. Windows Phone currently has single-digit market share for worldwide smartphone platforms.