Cannot See My World Book Under Shared in iTunes

I’m running iTunes on Windows XP and have a WD My Worl Book on the network. Every other feature of the World Book is fine (ie. I can access files, do backups etc) except I cannot see it in the Shared Section of the iTunes left pane.

The iTunes server is enabled (it was on as a default and I never changed this). I have placed mp3 files in the Shared Music folder.

Am I missing something here? Is there something else I need to do with the WD drive or in iTunes to get this to work?