Under Red Hat Linux 8.0 and 9.0, as well as SuSE Linux 8.1 and 8.2, use the "orinoco_pci" driver, which is usually automatically configured for you. Otherwise you can get a driver from the following website http://hostap.epitest.fi/.
The ThinkPad T40 system comes with a choice of three different wireless cards. Currently, the only card that is supported under Linux is the Cisco card. The driver is the same as the "ACU" driver listed above. The Phillips/Atheros wireless card and the Intel Centrino wireless card are not yet supported under Linux. For more information on Wireless and Linux, refer to the following How-To: http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wireless.html