This is in the Basement (PART 2) (UPPER)
area... when you first get to this location you can't get to this and instead have to take an elevator down.
In the Lower Basement area you learn to do the rotation and power switch thing and once you get to the other side of the room, you can get into another elevator.
Now you are once again in the Basement (PART 2) (UPPER)
area and from here you want to use the first rotation/power thing to go left and then use
to aim at a rotation switch for the next forcefield walkway to turn.
This walkway that you created is a straight line so you just have to defeat the sentry and can disassemble the box to get the VR Disk.