Hard drive locked

[monton]

Hello all
I would like to do a clean install of W10 but get a message that the hard drive is "locked". What does that mean and how do I unlock the drive?

 

[Cycloid Torus]

Please describe system and current Operating System.

Are you familiar with UEFI (http://windows.microsoft.com/en-US/windows-8/what-uefi)?