Reformatting the drive will erase all data on the drive, so you should copy any data you
want off the drive prior to formatting.
The following is based on Mac OS X version 10.10.5. However, the steps are suitable for Mac OS X 10.6.8 to 10.10.5. For instructions on how to format a drive in Mac OS 10.11 (El Capitan) and above click here.
To reformat the drive in Mac OS X:
1. Open Disk Utility
2. Select the Seagate drive on the left that shows the capacity
3. Select the Partition tab on the right hand side of the Disk Utility Window
4. Select Partition Layout and select 1 partition
5. Next to name you will see untitled 1 where you can name the drive. This will be the name
shown when the drive mounts.
6. Change Format to Mac OS Extended (Journaled)
7. Select Options and select GUID Partition Table
8. Select OK
9. Select Apply
You will get the follow window advising you that this is a data destructive process and any data currently on the drive will be deleted
10. Select Partition to finish the formatting process