Compare prices on Toshiba Portege Z20t-B Find deals from 5 shops and read reviews at Operating system (latest version). Windows 8/ Professional. The Official Toshiba Support Website provides support for Portege Z20t-B. What's my Operating System? Click the Start button., enter Computer in the search. If you use an operating system that was not pre-installed by TOSHIBA, some of the Short Model Name. PORTÉGÉ Z20t-B. Z20t-B. PORTÉGÉ WTB. WTB.