How to format a Seagate HDD to OS X Extended (Journal) with Disk Utility
In Disk Utility find the HDD you are trying to format in the left hand column. Select the disk and not the volume - that appears as child under it - to repartition it. 

Just choosing the volume erases or replaces the file system but not the partition table type. This may apparently fail if the partition map is mal-formed.



If you feel confident with terminal, you may use instructions from other topics, alike this one.