Try this in Disk Utility click on the Partition click on the Current Volume Scheme drop-down menu and select One (1 partition) from the Partition Schemes provided: Click on the options button and chose either the GUID Partition button or the Apple Partition Map button click OK Select other options as desired (e.g., Volume Name Format etc.). Click Apply the Partition Disk screen opens click Partition. At this point, the volume dismounts from the desktop and the drive is partitioned and formatted. When the new volume is created, Time Machine may open asking if you would like to use the volume for backups. Click Cancel to proceed.
This worked for me on a 1TB Free Agent Extreme.