hope your are not hide folders s/w !!
try using this
computer > (right click) > manage > disk mgnt..
check the partition table, hope its not corrupted due to reasons.
I have a HP dv8233 Pavilion laptop and it has a C: OS drive with all my regular computer files on it and then it has a D: Data drive labeled as data that I use to keep all my movies on. It used to work fine but now when I open it and click on the folder with my movies on it, it says that it is not accessible and access has been denied. What does it mean?