Can't use my internal HDD as external HDD, Media is write protected!

Hi WDTera, welcome to the WD Community. There are several brands and models for external hard drive enclosures, each one with their on list of compatible drives. 3rd party drive enclosures are not supported, but you can try to write zeros using DLG while the hard drive is connected directly to the PC motherboard. 

How to low level format or write zeros (full erase) to a WD hard drive or Solid State drive