I have a Windows 7x64 Ultimate, 6 GB memory, 1 TB HD. 3TB Barracuda XT HDD. The HDD is installed on a StarTech 4 bays external enclosure I had troubles so I converted to a GPT, created 1 partition and formatted as NTFS. The hard drive I can write and read to and from the hard drive but it will become unreadable at some point while I am copying files or after I have copied files to it.
I have copied large Bluray movies and diverse video files, I have also copied 32 GB of pictures, and I have copied about 86 thousand music files in different formats. At some point the partition becomes unreadable and I have to format the partition again (all files lost) and I have to start the whole process again. At some point I have been unable to copy large ISO (Bluray movies) file images.
I have partitioned the HDD in 2 partitions P1 - 2TB, P2 - 1TB and I have lost every single file in either partition the same way. I reformat the HDD and it seems fine.
I have run seatools to check the hard drive and it reports to be OK.