Having owned 2 Dell laptops, I know the frustrations of having to get wireless working in Xubuntu. It was after many re-installations later that I found out that the process is quite simple and it actually requires only on line in Xubuntu. Open terminal and type:
sudo apt-get install bcmwl-kernel-source
Atfer a couple of seconds you will be asked if you want to continue:
And you are done wireless will work not without you having to restart.
(Yeah, I know the screenshots say, Ilona instead of Roja. That is because I gave her my mini Dell and I reinstalled Xubuntu for her. Since she will be moving far away, from where I can’t help her I decided to write this tutorial for her, in case she needs to re install.)