help trying to download an ebook "error:check activation" HELP!!

For this problem, you need to deauthorize and authorize ADE again.

Mac:

1. Go-> Go to folder.

Go to folder dialog will appear.

2. Type   ~/Library/Application Support/Adobe/Digital Editions

drag the activation.dat file to the trash.

ADE will be deauthorized now.

Now Authorize ADE again [Help -> Authorize Computer].

Windows:

Choose Start > Run.

In the Open text box, type regedit and then press Enter. The Registry Editor opens.

In the left pane of the Registry Editor, locate the following registry key:

HKEY_CURRENT_USER\Software\Adobe\Adept

Right-click the Adept key and choose Delete.

In the Confirm Key Delete dialog, click OK.

Your authorization will be deleted.

ADE will be deauthorized now.

Now Authorize ADE again.