It’s extremely unlikely that you’d get two failures on two different modules like this, with the same failure state. Do you get the device connected sounds when you connect them ? Does device manager do an automatic refresh when you connect them ?
I just recently re-installed Windows 8.1 on my PC. When I read this post I thought I’ll try it out quickly myself. Plugged in my Medusa board with the USB Client SP Module. Windows detected it and installed the drivers etc and afterwards it appeared as COM7. I cannot think why it does not work on your PC.
Also, the battery module can only be used for power but not COM port. However it can be used for programming on the netmf devices, not medusa. Check the socket type.