Choosing an WLAN card
The first step in doing the upgrade is to visit your notebook manufacturer's website to find out what flavors of wireless LAN cards are supported for your notebook and to download the drivers for them. In my case, I visited Fujitsu's PC support site and found downloadable drivers for both Atheros and Broadcom-based cards (Figure 1).
Figure 1: Drivers for the Fujitsu S2020
(click image to enlarge)
TIP: Since Intel was so late coming out with an 802.11g Centrino, most notebook makers were forced to turn to other makers for their internal 802.11g WLAN boards. Broadcom was there to capture much of that business, with the result that you're likely to find that your notebook has a Broadcom-based 802.11b/g WLAN option - even if they don't identify it as such.
In my case, I downloaded both Atheros and Broadcom drivers since I had harvestable products with both flavors of cards.
Revised January 28 2005
A helpful reader had the following to share regarding sources of drivers for mini-PCI cards:
For the MiniPCI card used in the [Linksys] WAP and WRT, one should use the driver for the WMP54G PCI card as that card too uses the same MiniPCI card (again, first revision, later revs used the integrated chips). The latest driver for that can be downloaded from Linksys. In fact, the MiniPCI card will be detected as a Wireless-G PCI card, and it works beautifully!