I was unable to find you e-reader from your description, so I cannot check to see if it is Win 7 compatible, or if there are any special circumstances regarding using it.
Digital Right Management may not be a factor here, but any copyrighted material is handled differently in Win 7 in that there is more protection for copyrighted material. There is no page in Win 7, but when I used Audio Books in even Win XP, I had to register the computer to be able to play the audio books I purchased. I was just suggesting this might be a possibility in your situation, but I do not know that is your problem.