Background: I had a 500GB WD external HDD it broke I got it recovered to a 1TB WD passport external HDD. My oringal 500GB was readable on both MAC OSX and (with my Bootcamp) Windows XP I never checked the format but it was both readable and writable so I assume it was either FAT16 OR FAT32. However I knew nothing of Drive formats until my current problem. The new 1TB HDD came NTFS and I formatted it to exFAT on my brothers new laptop which has windows 7 not realising this meant it would automatically want exFAT because that is what it runs on I assumes FAT was FAT and the Mac would then write as well as read which it didn't do as NTFS. Now I want to convert from exFAT to NTFS so it is again readable on OSX. I know you can convert from FAT16/32 - NTFS without formatting the drive my question is can you do the same with exFAT I have alot of data so I don't want to mess up my drive. Please let me know if you think this is possible.