To get an Aironet 16-bit PCMCIA card working with the WPA-supported drivers, the firmware must be upgraded.
I found it was difficult to do this, so I put together a live CD that accomplishes it. It has a few bugs but will work. You will need a Windows 98 Second Edition CD handy in order to supply files that are not in the live CD image. The firmware will be version 5.30.17 which is not the latest but is good enough to support WPA with the Linux driver. (With an XP live CD you could install the latest 5.60.22 firmware, if XP will run on your laptop you are using this old 16-bit card on, and if you have some other media on which to access the drivers while the BartPE or other XP livecd is inserted.)
Download and burn the attached ISO file as a CD image. Boot from the CD or use a Smart Boot Manager on the All-In-One Boot Floppy, or similar program to chain-load the bootable CD.
Aironet Upgrade Win98 LiveCD ISO
When you boot up the CD, you’ll immediately encounter an “Abort, Retry, Fail” error when a DOS extender attempts to create a swapfile on a non-existent drive C:. Just “F”ail it and it will continue.
Next, Windows will attempt to discover devices. You must be careful here or the live CD will fail to start up. (If the live CD fails to start up and you have a hard drive with a Win9x partition on it, remove it temporarily.) The first query you will get is for a missing lmouse.drv, lmouse.vxd, and/or lmul.vxd. Just hit ESC to cancel the dialog.
Then you will get a PCMCIA configuration wizard. Just accept all the defaults. Windows will ask for the Win98SE CD. Swap the CD and hit OK. After copying files, Windows will come back and complain about not being able to read from drive A:. Swap the live cd back in and hit Retry. You will get the PCMCIA configuration wizard again, just accept everything as before.
Windows will then restart after flashing a spurious MBR virus warning message. If you did things right, you will make it to the desktop with functional PCMCIA (check Device Manager to confirm the PCMCIA sockets are happy).
Insert your Aironet card. Then by way of either installing the driver when prompted, or going to Device Manager and updating the driver, use the Have Disk method of locating the driver and point it to the X:\cisco\PCI-PCM\9x-Me-2K folder and select the netX500.inf. Select the Cisco Systems 350 Series Wireless LAN Adapter. Then you’ll have to point Windows to the same folder again to install the driver files. Once you have done that, the adapter should be good to go. Do not allow Windows to restart. (If a restart is really needed, go to Start->Shut Down and then use the keyboard to navigate to the hidden second option which will quick-restart.)
Now browse to the X:\cisco\Aironet Client Utility folder and run the windgs.exe. If the adapter is happy, the program will say “Your 350 Series is Not Associated!” indicating that the card was found but it has no connection. If the adapter is not happy, try removing and re-inserting it.
Click on “Load Firmware”. Browse to the X:\cisco\PCI-PCM\Firmware folder and select the pcx500b.IMG firmware file. Once it flashes, you are done and can proceed to getting the driver working in the above link.
Note that you can flash this firmware on a Cisco Aironet 340 or Dell Truemobile 1100 as well. These cards are marked AIR-PCM340 and in smaller letters AIR-PCM342. At present, the Linux WPA driver will work on the Cisco card but not with the Dell card for unknown reasons.