Throwback Thursday: Windows Mobile 6.5 - Thurrott.com. By the time Windows Mobile 6.5 came around I had already given up on Microsoft's mobile OS. As one who followed and had access to Microsoft's OS development from 1997 through 2006, I am convinced the fatal flaw was Microsoft's insistence that Windows CE/Windows Mobile look and work like Windows desktop. If Microsoft had accepted the input that handheld devices and phones demanded a much different UI in 2000, it is very possible they would still be at the top of the mobile phone market. They were convinced they were right, but sadly they were very, very wrong.