Recognizing Memory Card in e-Reader

I have an Aluratek e-reader and Digital Editions will recognize it and I can easily download books to it.  However, this reader has a slot for an optional memory card (up to 6 GB) and Digital Editions does not seem to be able to recognize that there is a memory card there.  I have to continually delete all the books on the Aluratek's internal memory (which is quite limited), down new books there and then transfer them to the memory card.  This can be frustrating and time consuming.  When I was still running Win XP on my computer, I did not have this problem but it occurs when running WIn 7 and Win 8 and I cannot seem to resolve it.  Any suggestions are welcome.  Thanks.