Lenovo ThinkPad X. The ThinkPad X is a line of notebooks and convertible tablets originally manufactured by IBM and now sold by Lenovo. Thanks to its smaller size and excellent battery life, the X Series is a clear choice for business people on the go. Every professional chooses the X series thanks to its workmanship, versatility and great safety features. IBM announced the ThinkPad X (initially X20) series in September 2000, with the goal of providing "workers on the go with better options for working with extra-thin and extremely light mobile computers." The first ThinkPad X-Series product to be released by Lenovo was the X41 in 2005.