I'm using GOverlay 1.6.6.4 under Windows 8.1 Update 1.
I'm using HWiNFO to gather sensor information such as CPU speed, memory, GPU, network information, etc. And when I did a quick sensor search for the "disk" keyword, it's only detecting one hard disk, which is the USB hard drive. Here are a couple of screenshots that I provided:
The HWiNFO plugin is improving. However, it needs more work in detecting more than one hard disk.
I'll upload a screenshot of what my GOverlay layout looks like and what is missing right now.