I got this external HDD from WD formatted as NTFS. I'm trying to share files from my PC to Mac using this external drive but when I get files from my pc to the external drive and try transferring them to my Pc from the external drive i get something like "you do not have sufficient permissions to do this task" when i check the info it says that I only have READ permissions on this external drive. even if i give everyone permissions on my PC for my MAC does not work. How can I change the permissions??