How to format a Seagate HDD to OS X Extended (Journal) with Disk Utility I have just got a new external hard disk, the Seagate Expansion 2 TB, and I am trying to format it to work on my Mac. I was told that I had to erase the disk and format it to OS X Extended (Journal) with the Disk utility program. 

However, Disk Utility won't allow me to erase it, and the partition button is greyed out. I will attach some screenshots of the problem:

 


Any help is appreciated!
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.