I have almost exactly the same question - but you're advice doesn't quite do the job. I Authorized my PC a long time ago and used my e-mail address at the time. That address has been defunct for a long time and I would like my ID to be current.
I followed the instructions and now I can't access my books. (I SEE now that you mentioned that) So does this means that they are gone forever?
Also I can't authorize my PC for ADE now. So my old ID is gone and I have nothing. Why would anyone want to do this?