Tolino Shine doesn't allow deleting or adding books

Dear all

I've been given a tolino shine as a gift with already some books on it. I now wanted to remove the books I've already written by moving them to my computer and of course adding other books.

My Windows 7 PC recognices the Tolino and I can access all folders withhin. But what ever I do - copying books in or deleting some - the changes are not made on the tolino.

I than installed calibre on the PC in the hope it would work with that. But nope. The same situation!

I have also given access to the library on the tolino - without effect.

What do I do wrong - or what does the trick?

I'm sorry if this question has already been ask but I didn't find it with the search...

Thanks a lot in advance!