You will probably need to reinstall, deauthorize (ctrl-shift-D, cmd-shift-D on Mac), and uninstall again.
Thank you. That successfully removed my Adobe ID from the ADE on my notebook computer.
Now I want to use my Adobe ID on another computer and it won't let me. It says it can only be used on one computer.
Why is it so hard to get content onto my Kobo reader?
It is hard because Adobe has made a complete pigs breakfast of implementing the ADEPT DRM infrastructure and the ADE software.
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