I have the Prydain Chronicles by Lloyd Alexander wishlisted in hardcover, but the HC and PB copies have the same ISBN.  Every time a book is offered to me, I have to PM the sender first and ask if theirs is HC or PB.  Every single time, it turns out that it's PB, and they posted it wrong.  I have had this happen like ten times, and it's starting to get annoying.  Is there any way to change this to two separate listings in the database?

I don't believe that it can be changed. From what I understand, if the book shares the same ISBN number, the member posting should pay attention to the binding listed in the database. For example, for the book your looking for, if the binding in the database says paperback, the member posting a hard back must post their book without an ISBN number since their binding doesn't match what is in the database.

This is what the Help Center says on the issue.  Sounds like you know this info already, but these people should not be listing the paperback version under that ISBN, they should do a customized listing.  There is no way to change the way this is done through PBS because the publisher assigned the same ISBN to both books, so it's up to the posters to follow these instructions.  I'd let them know about this if I were you.

Problem: You enter the ISBN on your paperback and the book Listing Preview says "hardcover".

This means one of two things:

1.  Your book is an Advanced Reader Copy (ARC)

If your book is a paperback, and the ISBN brings up a Book Listing Preview that says "hardcover", please check your book to be sure it is not an ARC.   If it is an ARC, it cannot be Posted for swapping at PBS.

Solution: You can offer this book to others in the Book Bazaar Discussion Forum, but you cannot Post it to your PBS bookshelf.

2. The publisher chose to assign the same ISBN to more than one version of this title.

Publishers sometime choose to assign the same ISBN to multiple versions of a book.  However, PBS can attach only ONE booktype to the listing for an ISBN.  If your book does not have the booktype assigned to the ISBN in the PBS database, you will need to post it with a customized listing, using the Post a Book Without an ISBN link on the Post Books page, so that the booktype matches your book.

Solution: You will need to post this book with a customized listing for the book, using the Post Books without an ISBN link on the Post Books page.

Nope there is no way to split it since they share the same ISBN.

I had a HB that showed that the ISBN assigned to it was a paperback.  I was advised (told) that I needed to back the book out and to post it as NO ISBN.  This was very unfortunate, as I was never able to get the book to move and finally just withdrew it and gave it to the library.  There was no way to post it under it's listed ISBN correctly. 

Pat O. did you post the book in its specific genre...that you had that one available with a different cover...was it a WL book.  I've been able to move mine that way when they are a WL book.

It's becoming more and more common to post your PBS-assigned number as a tag to the other editions of the book. Something like "also available as HC under #295986" or whatever the number is. Then people can decide if they'd rather have the other binding and come find your's instead. I've heard several people comment that it works well.

Also, it is important to put an image and good description on non-ISBN listings, as they are harder to find on the Internet without the proper ISBN. If there is another edition of the book listed, already, I usually open the window to the already posted on, and the window to the Post a NON-ISBN page, and highlight and drag the infomation from the one to the other that is relevant. Then copy down to my hard drive the image (if it's good) and then upload it to my non-ISBN copy. Makes a definite difference in whether they move or not, if they have images and descriptions.