Well after several attempts I finally got to install ROS 5.14 on this board using netinstall. Firstly the computer that I had first tried with did not support PXE, so I had to use my netbook. Secondly I had to use an ethernet crossover cable between the netbook and the RB. After that I was able to complete the activity with the instructions at the website.
I am now back to square one where the Wireless card are not identified. The RB seems to be faulty because at tmes the card are identified. I tried another board and it worked without problem.
Thanks for all your input/responses.