To flash or debrand this model, you must use SETool box or pay servers like D-Client or Da-Vinci.
It's cheaper with D-Client. Just enter http://www.cruisersuite.com and download the files for your W910 according to your language needs. Top Sony files will not work with D-Client, only with SETool box.
The latest version, as URBANO said, is the R1FA035.