Okay, in order to run the other diagnostic (SeaTools) you need to set the drive to ATA, it will then be recognized.
Of course, if you have a drive other than a Seagate, you will need to use that drive manufacturer's diagnostic tool.
The Dell diagnostic runs a basic S.M.A.R.T. test to determine the drive's health. I would recommend a full diagnostic using the utility provided by your HDD manufacturer.