How do I move my Digital Editions to a new computer

Go to the site www.aractivate.adobe.com (or just go to File/Digital Editions/Activate Device...)
Login there with flv converter same ID you used before.
Push the activate button
If you see a screen about Could not find

Is there a way to de-authorize a computer, as over time your 6 activations would run out (new computer/upgrade/new hard drive etc)?

Digital Editions 1.5 "solves" the portability issue. You can copy your books (assuming the publisher allows it) onto up to 6 computers and 6 devices. All you have to do is authorize your computer with your Adobe ID.

I think I read somewhere that the next version (I think 2.0) will have all this solved? I don't need to read anything right now, just want to make sure I'm able to access it in the future. Thank you for the wonderful instructions. Hopefully other users with the same question will read this.

Is it OK to have both Adobe Reader 7 and 8 installed at the same time?

There are two possibilities here:
1. The user did activate their old system (where the books were downloaded) with Reader (or Acrobat 7) using an Adobe ID or Microsoft Passport.
2. The user did not activate their old system

First case:

In order to activate your new system, you have to have Reader 7 installed. It is the piece that actually does the activation. So here's what you need to do:
Get Reader 7 here http://www.adobe.com/products/acrobat/readstep2_allversions.html.
Log into your computer (assuming it actually has a login but they do need to be in the account that you used when you bought the ebooks)
Start Reader 7
Go to the site www.aractivate.adobe.com (or just go to File/Digital Editions/Activate Device...)
Login there with the same ID you used before.
Push the activate button
If you see a screen about Could not find Reader software blah blah choose Yes, my computer does have .. Blah blah.
Reader 7 should then handle the edn file sent down and tell you that your computer has been activated. If for some reason the EDN file isnt handled automatically, just tell the OS to have Reader 7 handle the file.
There will be a pause while Reader does its thing. Then you should be presented a dialog telling you that your computer is activated.

Second case:

If the user did not activate their old system, there are several possibilities:
The user no longer has access to the old system (disk reformatted, lost, left company, etc.).
o In this case, there is no real hope. The keys required to open the book were on the old system. Even we cannot retrieve them.
The user still has access to the old system In this case, they should do the following:
o Activate the old computer using the exact same procedure as outlined above for the new computer, using an Adobe ID (they could use a Microsoft Passport, but even Microsoft deprecates it now and they will need an Adobe ID for Digital Editions 1.5 anyway).
o Then proceed as indicated for the first case and activate their computer using the exact same ID

Both Cases:

We then recommend that you install Digital Editions 1.5 Beta, which will then convert your books to the enhanced DRM format which makes them portable.

After repeating the steps on your new Mac you should be able to open your books. Then upgrade to Digital Editions 1.5:

http://labs.adobe.com/technologies/digitaleditions/

More info about it is available here

http://blogs.adobe.com/digitaleditions/2008/02/digital_editions_15_beta_is_re.html

And here

http://blogs.adobe.com/digitaleditions/2008/02/digital_editions_and_content_p.html

This is a little involved but should work. Let me know how it goes.