Is it showing up as an external drive or similar in Explorer?
For most Sonys you need to install the Sony Reader software even if you don't want to use it. It also installs a driver that is needed for the Sony to be recognized by ADE. (Silly that that is necessary. Sony make good hardware, but they have always let themselves down on the software side.)
Some Sony's don't work well with ADE2.0 and Overdrive library books. If you have an issue there, try installing 1.7.2 instead.
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
The forum software is sometimes corrupting the link above. There shouldn't be a blank in 'editio ns.html'. The following redirects to the same page: http://tinyurl.com/diged172
Thank you for your help. That fixed it.