I'm not sure how it will work exactly,
but it looks as if you have to visit the vendor sites (www.millsandboon.co.uk etc) on the phone and logon there.
It appears you can buy yet more books that way ( http://www.millsandboon.co.uk/ebooks.asp )
and it may smooth the way to reading the books you already have.
I think the books from other vendors are locked using Adobe DRM technology,
but with your id from the bookseller and not your generic AdobeID.
Once you have registered the bookseller id on the phone, you may be able to read all the books from that bookseller.
All this is ???
If anyone knows a page that describes how Adobe DRM works across different vendors etc,
and the relationship between different registrations, I'd be very interested if they could post it.
You are pretty much out of look for being able to read your old content.
You started of with an anonymous id (let's call it A1). Your 'over 100 ebooks' downloaded before you did any thing else are licensed to A1.
You then authorized a phone with an Adobe ID (let's call it A2)
You then authorized your computer withing the Adobe ID Changing the id from A1 to A2. At this point you can't open content from A1 anymore. There error E_LIC_ALREADY_FULFILLED_BY_ANOTHER_USER
are saying that the content is licensed to A1 and you are trying to access them as A2.
Since A1 is anonymous there is no way to authorize it to any device, so you can no longer read any content licensed to A1.
Your best bet (which is a bit of a long shot) is to try to get your original content licensed to your AdobeID (A2). To do this you need to get new download links from where you purchased the content - and the magic phrase is that you need a new 'transaction id'. (Your current download links will have a transaction id that is point to the current license which is tied to A1).
The lesson for everybody else to take from this is - DONT ACTIVATE ANONYMOUSLY - YOU WILL REGRET IT.
I am afraid Jim Lester is almost certainly right if you keep within the direct use of ADE.
However, there are programs such as epubee (search on Google) that will remove DRM from Adobe DRM books.
It is not clear what the legal position is; and varies from country to country.
I understand that DRM stripping is not technically illegal in the US, what is illegal is selling or otherwise profiting from DRM stripping.
Whatever the legal position in your country, I feel that the moral position is clear. If you are using it to overcome technical issues with Adobe's horrible implementation of DRM rather than subverting the intent of DRM, it is the right thing to do. That might well be the only way that you can use your books in the way that you quite reasonably want to.
The DRM stripping programs won't do Rochemma much good at this point. In order for them to work, you have to be able to open up the book.