Hi Have a 3TB Seagate Barracuda XT model ST33000651AS formatted on a Windows 7 machine 3 years ago with one 3TB GUID partition (GPT) using NTFS. The drive is fully recognized by several Windows machines I have plugged it into using different USB enclosures. When I was connecting some of my old hard disks today to my MBP (early 2011) with Mavericks using 2 different USB enclosures I got a message on connecting the disk to the Mac that read something like this: This disk must be initialized by Disk Utility. I pick ignore as I was not in the mood of losing 2.5TB of data. When I went into Disk Utility I saw that the disk was shown as a 800GB hard drive. None of the other 6 NTFS hard drives I tested before this one gave me any problems, but they were not GPT disks, they were MBR disks. Is it not possible for the Mac to access GPT NTFS disks with partitions >2.2TB that come from a Windows environment? I tried 2 different USB enclosures that worked totally ok under Windows without any success under OSX. Is it a compatibility problem with GPT disks created on Windows, or maybe with the Seagate disks? Thanks.