I have Windows 8.1 on one HD. I installed Windows 10 on another HD. I have a 3rd HD where I store music, photos, movies, and other stuff. When I finished installing Windows 10, I could access all my files on the 3rd HD. Then I rebooted into Windows 8.1. There I couldn't access any of the files on the 3rd HD. The security descriptors had changed. So I changed them back and was able to access the files again. Then I rebooted into Windows 10. I couldn't access the files on the 3rd HD. Is there a way to allow me to access the 3rd HD files from either OS without having to change the security settings over and over?