I would never throw out the Word of God, even if it was missing 7 books.
Indeed!
I have several Protestant Bibles from my childhood as a Protestant, including ones given to me by beloved relatives. It has never occured to me to do anything other than treasure them and preserve them.
As to what to do with the other Protestant books, I would ask not so much whether they have errors, but whether they have some merit apart from the errors. There are certainly Protestant books which have scholastic and theological merit, despite some differences from Catholic teaching. Catholic writers, including Pope Benedict are happy to reference Protestant theologians in their writings - so presumably their libraries include these books.
So, if the books have some scholastic or theorogical merit, then keep them or dispose of them respectfully, such as donating or selling them. Also, they might have some personal importance to you, eg. given by a friend, in which case keep them.
I retain many books by Protestant writers which pass some of these tests. eg. *The Hiding Place *by Corrie Ten Boom, and
Hind’s Feet on High Places.
I also have a few Protestant books (and Catholic ones!) which have little value to me now, but have sentimental value simply because they are part of my journey. When I see them on my bookshelf I am happily reminded of where I was years ago.
If, after this, you would feel most comfortable with disposing of them, then I recommend that, rather than disposing of them, you give them to a Catholic friend to retain for, say, a year, while you think about it.
This is similar advise to that I give to people who are unsure about what to do with the pre-conversion DVD collection, ie. if you are uncertain then delay the decision by depositing them with a friend.
Continuing the analogy with unwanted DVD’s, then there may be some items which you have no doubt must go. In that case, do dispose of them. This is less likely to be the case with your books than some DVD’s.