This update is required if new battery packaging has firmware update required note on it. (HC-100 only). If HC-100 has OS 1.8.3 or later this update is not required.
First make sure you have the charger connected to your HC-100.
Then follow the instructions on the following guide (WMDC-fixes-for-Win10.pdf also attached) to get Window Mobile Device Center (WMDC) working properly on your PC, especially if you've never connected the HC-100 to that PC before: WMDC FIX
After the step above you need to connect your Micro-USB to USB cable to your HC-100 and to your PC to get it recognized. Launch Windows Mobile Device Center and verify it says CONNECTED (see pic below).
Now you should be able to browse the folders on your HC-100 controller via windows explorer on your PC.
Download the zip folder from the following website to your PC: https://junipersys.com/data/support/archer/ar2-os-191/Archer-2-OS-191-English.zip
Copy and paste all the files in the zipped folder to the root folder on your HC-100 via windows explorer. The HC-100 will show up as a storage device, just make sure you paste the files on the very top-level location of the HC-100 (once you see the first folders).
Then click and hold the power button on the HC-100 until you see the power menu. Then click the Reset button, this will restart the HC-100 controller. This will automatically start the OS update process.