Hi,
Have you made any changes to the computer prior to this issue?
I would suggest you to follow the below methods and check if it helps.
Method 1:
Try running Hardware and Devices troubleshooter and check.
Refer: http://windows.microsoft.com/en-us/windows7/Open-the-Hardware-and-Devices-troubleshooter
Method 2:
Check your hard disk for errors:
http://windows.microsoft.com/en-US/windows7/Check-a-drive-for-errors
Note: While performing chkdsk on the hard drive if any bad sectors are found on the hard drive when chkdsk tries to repair that sector if any data available on that might be lost.
Method 3:
Initialize the disk in Disk Management.
Create and format a hard disk partition : http://windows.microsoft.com/en-US/windows7/Create-and-format-a-hard-disk-partition
Note :Converting a hard disk partition or volume from NTFS to FAT32 requires that you reformat the partition, which deletes any data on it. Be sure to back up any data you want to keep before you begin.
Method 4:
Try connecting with different computer and check if it helps.
If the issue is still persist, then it would be better to contact the Seagate for further assistance.
Seagate Support: http://www.seagate.com/www/en-us/support/
Hope the information is helpful.