How can i get passport to work on mac

i keep getting an error- passport can not be modified.  i am trying to copy files over to the external drive

What Passport are you using? It maybe formatted for Windows if so it will be read only on Mac. If the drive came formatted for Windows then reformat it on Mac or download NTFS-3G http://mac-free.com/download/NTFS-3G.html Then drive should work on Mac and Windows.

Joe