How do i fix unknown, not initialized and unallocated external hd?

OK. One reason why Seatools is not seeing your external drive may be because there is that mysterious CDFS partition on that drive.

Before trying to format the drive, let us see whether Linux booted from a pen drive can see your external
disk and whether Gparted in it can see the CDFS partition and delete it.

For the present unplug your problem external drive.

Download Lucid Puppy (Ubuntu-Compatible Build) lupu-528.005.iso I have chosen this because it is only a 132.6 MB download. http://puppylinux.org/main/Download%...%20Release.htm Create your bootable pen drive with this ISO using Rufus 1.4.10 (616KB) Rufus - Create bootable USB drives the easy way (Before you run Rufus, backup all data on your pendrive for it will be lost when Rufus formats the pendrive during the creation process.)

Once you are ready, shut down your PC, plug in your problem Seagate drive
and boot from Live Linux Lucid Puppy USB pen drive.

Check whether your problem Seagate drive is seen by Linux and report.

For familiarising with Lucid Puppy read
Lucid Puppy way to recover files from a non-bootable computer

In that thread,

You will only see the screenshots from the time Lucid Puppy boots to the point where and how to identify your system drive and the external HDD . Your external HDD may or may not appear and that is what we are trying to ascertain.

Just report whether your 500 GB Seagate external drive is seen.