From the Ubuntu 10.04 Lucid Lynx repositories download following packages:
blacklist bcm43xx blacklist b43 blacklist b43legacy blacklist ssb
sudo mkdir /opt/drivers cp bcmwl5.sys /opt/drivers cp LSBCMNDS.cat /opt/drivers cp LSBCMNDS.inf /opt/drivers
It is best to get Windows drivers from CD attached to the wpc54g card or to download the drivers directly from an OEM website. If for any reason you cannot do it, then you can download drivers from here: wpc54g_drivers.tar.gz
Run the application ndisgtk by choosing menu: System | Administration | Windows wireless drivers. And then:
Open menu System | Preferences | Network Connections,
and select tab Wireless and there click Add button.
In a window that appears enter SSID of Access Point that You want to connect with,
choose Mode to Ad Hoc and type in Wireless Security data.
Click Apply button.
From now You can connect to your wireless network.
To load driver at system's start-up apply the following command:
sudo ndiswrapper -m