I’ve been wondering why Microsoft’s decision makers choose to use Microsoft Windows for tablets instead of the Windows CE platform that underlies Windows Phone. Windows CE was designed for devices like tablets that benefit from lower hardware requirements, lower power use, increased security, and instant on-off (suspend-resume). A Windows CE based tablet would be lighter and less expensive. More importantly, every piece of software written for a touch display. You could argue that the Metro-only ARM based tablets would have software designed just for tablet displays too. But, is a computer that can’t run “legacy” Windows software of much use? The point of using Windows is to access all the software available right now.

However, if you look at PC shipment numbers, Microsoft’s tablet strategy and statements like There’s nothing more important at Microsoft than Windows by CEO Steve Ballmer make sense (Network World).

U.S. PC Shipments Slip 6 Percent In Q4, While Apple’s Jump 21 Percent

U.S. PC shipments by the top 5 vendors was down 5.9% (this includes Apple Macs) in Q4 2011 while worldwide shipments were only up 0.5% (Apple is not in the top 5 worldwide).

PC shipments are flat at best (worldwide numbers). This means that Windows sales are probably flat too (not accounting for people upgrading PCs). Assuming that tablet sales (mostly the iPad) is a partial factor for this situation, putting Windows on tablets could help prop up Windows sales. This assumes, of course, that people are willing to buy ARM-based Windows 8 tablets that cannot run the non-Metro software that they use right now. If the answer is yes, Microsoft might see “PC” shipment growth revive (with the addition of Windows tablets). If not, they forfeit the tablet market for the foreseeable future.