Branching this to a separate discussion as the previous discussion was in regards to downloading books into ADE. That user already had ADE installed sucessfully.
Do you receive any error messages when you are trying to install Adobe Digital Editions?
Not sure of the exact wording of the message but it mentioned repairing the installation.
It may be worth trying an older version.
There have been quite a few issues with ADE2.0; though I don't recognize your problem as one of them.
You can get 1.7.2 from the Adobe site. Much more reliable than V2.0 in many ways.
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
I uninstalled ver 2 and tried to install ver 1.7.2. That didn't seem to work so uninstalled that one. Reinstalled ver2 and it seems to be working now.