I have an old Dell D620 that I use as a sofa surfing laptop. I've found Ubuntu works great for this purpose. I've freshly installed Ubuntu on it a few times and always have a problem with the wireless drivers not installing correctly. To fix this run these two commands from terminal:
sudo apt-get purge bcmwl-kernel-source broadcom-sta-common broadcom-sta-source (it may not see all of these)
sudo apt-get install b43-fwcutter firmware-b43-installer
Restart and wifi will be good.