Thank You for the help.
The links that You gave me are for windows 7, instead I have windows 8.1, so I will not try those drivers.
Also, I have "solved" this issue.
On the same pc I removed the original hard disk with windows 8.1 and then I installed a new hard disk, where I installed windows 7.
With windows 7 I had no problem with the board.
I removed the hard disk with windows 7 and put back the original hard disk with windows 8.1 and, magically, the board worked!
Thank You again and regards
Rodolfo Giovanninetti