The message is telling you that you've downloaded the ebook with a
different ID - which you figured out. Unfortunately, the download process
embeds information about the user at the time of the download, and cannot
You could, however, change the computer user's ID using a combination of
keys to de-authorize ADE under your current user ID, and then re-authorize
it under the old one (I think - if the old one's not valid, I don't know
what ADE will do). If you do this, then you'll have to repeat the process
with every ebook you've downloaded under the old ID - and do it in reverse
for all those ebooks you've downloaded under the new one.
You don't have to be computer-savvy. All you have to do is to read the
HELP section in Digital Editions, where the key combinations are explained
for Windows PC's and Macs. You can get there from the Library or Reading
views in Digital Editions by using the F1 key. There's more information
that you might use later in the HELP section, such as an explanation of how
Digital Rights Management will work and how you'll see it if it does.