well it should show up under my computer as a lettered drive. But if you goto this link
http://esupport.sony.com/US/perl/swu-list.pl?mdl=NWZS618F&LOC=3 and select your operating system you can find a firmware update. As well as find software to use. If you update your firmware you should be able to fix this problem from happening in the future. If you are unable to update the firmware due to it still not showing up on the computer.
you may have to reset it to factory setting. this problem was possibly caused if you formatted the device on the computer and deleted its usb PNP settings. Instead of formatting it through the device.
to reset the device back to factory settings you..
1. press and hold the back/home button in the pause mode until the home menu appears.
2. press the directional buttons to select the settings icon (looks like a suitcase) then press the play/pause button to confirm.
3.press the directional buttons to select the "common settings" and then press the play/pause button to confirm
(the list of common settings options will appear)
4. press the directional button to select "reset all settings" and then press play/pause button to confirm.
(the confirmation screen to set back to the factory settings will appear).
5. press the directional button to select "yes" and then press the play/pause button to confirm.
("restored factory settings" will appear)
for reference you can find a copy of the user manual by
clicking here.
If you need further assistance please feel free to follow up with a comment and i will be here to assist you. If this assisted you please feel free to rate the comment 4 thumbs up. thanks and have a great day.