Bit of an experiment.
I have 2 x ASIC Miner Block Erupter 333Mh/s Rev. 3.00 plugged into powered USB ports.
I've downloaded and installed CP210x_Universal_Windows_Driver from https://www.silabs.com/products/development-tools/software/usb-to-uart-bridge-vcp-drivers.
If I run bfgminer, I receive an error
"no devices found. Press 'M' and '+' to add". I press
+, but no devices are detected.