I think I ran across some info at one point that with some updates you can get original AirPort cards to work with WPA while running under OS X but they'll still be stuck at WEP under OS 9. I don't think I've ever really bothered to try the OS X thing though. 802.11b really should be run on its own network for maximum compatibility and isolation from critical data; if this is the case then WEP would be fine unless perhaps you're in an area with persistent script kiddies trying to break into wireless networks day and night. I remember years ago when I lived in an apartment, running WEP for older hardware support, and even with most security settings enabled it would eventually get hacked via WEP encryption attacks and MAC cloning, so I just gave up on legacy wifi (my room was tiny anyway so cables weren't a huge deal, but it was easier to get Mac-compatible wifi cards than Mac-compatible Ethernet).