i have a my passport ultra. the file on it were from a PC. i only have a mac now. i want to delete some of the files but it does not appear that i can do that using my mac. can you help me understand how to delete the files
If the drive was in windows file system i.e NTFS the files cannot be modified or deleted from the drive using MAC as Mac can only see the drive as Read-only.
Take a backup of the drive and reformat it to HFS+ to use it on Mac.