I am trying to tranfer library books from adobe digital to my kobo.

[Guest]

When I try to authorize my computer the adobe tells me that I can only authorize this computer with an Adobe ID that hasn't been previously used to authorize any other computer.

[sjpt]

Unfortunately, ADE is a completely rubbish program.  In this case ...

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Sometimes ADE gets its registration/activation confused and in a semi-authorized state.

Uninstalling and reinstalling does not help.

Unfortunately, it often then gives misleading error messages about what is wrong.

A common incorrect message informs you that the ID is already in use on another computer and cannot be reused.

This can often be resolved by completely removing any authorization using ctrl-shift-D to the Library screen on ADE (cmd-shift-D if on Mac).

Restart ADE, and then reauthorize with your (old) Adobe ID.

In extreme cases on the mac, the following extra step has helped some people.  Navigate to /Users//Library/Application Support/Adobe/Digital Editions and drag the activation.dat file to the trash. If you are using 10.7, see Access hidden user library files | Mac OS 10.7 Lion. http://forums.adobe.com/thread/1265248?tstart=0