I purchased a Seagate Barracuda 500GB HD about three or four years ago. It is formatted as NTFS, but I installed the free driver for Mac compatibility. It worked without issue for the first few years. However, it now makes a weird grinding noise - like the disc is accelerating then decelerating - and it takes about 10 minutes (literally) for the drive to be detected/mounted. Once the drive actually mounts, it works fine (no grinding noise, files transfer properly). What might be causing this problem and how can I fix it? Should I be concerned that my HD is about to go, or might this be an enclosure issue? The enclosure is a 'Smart Drive', which I purchased for about $30 back in the day. Thanks for the help.