Borrowing a PDF ebook from OpenLibrary, the first time for pdf. (I have borrowed a few epubs from there previously, about a year ago.) Digital Editions is authorized for this computer (only), and from the Help menu, I can display my Adobe ID / Account Number.
EDITED TO ADD VERSION INFO:
I am running ADE v 2.0.67532. I do not wish to upgrade to v. 3.
The computer is a 32-bit Hewlett-Packard running Windows Vista Business.
Upon trying to load the acsm file into the Digital Editions library, I get error message "Error! Check Activation" and the book fails to download. There is no error code provided in the message box.