You have to install again on the 2nd hard disk and only select pts, not the live game. Youll have to place the installer on the disk you want to install the pts on. You’ll end up with 2 separate installs with 2 launchers - 1 for live and 1 for pts. And iirc they cannot be running at the same time. I did this last year before morrowind pts dropped, and I remember it being fairly easy.