It is NTFS. If I copy the drive contents to the G5 HD then reformat the external drive and reload the files would there be any problems? How would the Mac recognise the file structure from a Windows HD (there is no operating system on the external drive only mp3 files). Could I then, say, take the HD to a party and play the mp3 files on a Windows based system? Sorry to ask basic questions but as a beginner it's best to ask those who know.