I’ve just bought a NWZ-W273S to listen music while swimming training. While it’s extremely easy to add songs (just drag&drop in Music folder), updating to 1.10 firmware proved to be impossible. It didn’t work on Mavericks, XP or Win7.
So after countless tries, I dig to the temp folder and copied the ~20MB “firmware.sb” file. Just like updating a Sony camera, copied the file to the root of the device, and powered off and on. The led rapidly blinked red and it turned itself off. When I plugged in again and checked the Information.txt file, the firmware showed 1.10. Success!