The old HDToolBox always reports large disk sizes wrong. Ignore that.
Add the partition like you would normally (remember the system partition must remain <4GB area). Then continue to install 3.9. Once the AOS 3.9 is installed and running, you can add partition(s) to cover the rest of the disk.
Do NOT attempt to access any partitions >4GB area unless if you're under OS 3.9. Always quick format the partitions, never do full format.
