I can only see 1.5TB of my 4TB hard drive. How do I fix this?
I was able to fix the problem myself.
Recall from my question that I had the new hard drive connected to the computer via an usb board from an old external hard drive. I circumvented using that and plugged the new drive directly into my mother board. I was able to format the entire 4TB of the drive as expected. Oddly, I took the new drive out and put it back in the old usb board and windows has no problem seeing all 4TB. The board must have just had a problem reporting the unallocated space to Windows. Thanks to the others who answered or commented.
Since July 2015 to March 2020 I've been using a USB 3.0 to SATA Hard Drive Duplicator/Clone Docking Station for 2.5" & 3.5" HDDs. I've yet to use the cloning feature, but I accessing the HDDs is simple. I just slip them in the top slots and connect via USB to the computer. The one I have has an explicit 12TB limit. I've successfully used and allocated fresh 8TB drives many times. One concern I've had is over heating when copying a lot of data that will take many hours. In those instances, I set up an external USB fan to blow on the drives.
The one I have doesn't seem to be available anymore, but there's a lot of options now. This is mine:
