It is stated (after a safety alert symbol and the word WARNING) that drives must be set to "Master" and place the jumper in this position before installing into the box!
In my case, Windows SEVEN did not recognize the two DD (master jumper) that I wanted to install :(
My third test (with DD WITHOUT jumper) was recognized, installed and ready to use right connected USB plug ...
So I turned on my 2 riders DD "défecueux" and many took me recognition and immediate installation without history (
Next time, I will as usual; I will not read the instructions!
So only 4 stars for this product, which, however, seems to me a good practice ...