I am guessing you just need the router password protected so the average joe won’t steal the internet.
If this is the case, set the security settings in the router to WEP 64 bit. This will require a 10 digit key (I typically just use a phone number). You should have no problems getting any of those computers to connect to a WEP- protected router.
If you want it a bit more secure, setup the router using WPA security (NOT WPA2 – WPA2 is more secure but some older cards may not support it). not sure the character requirements on that one but you should be able to use the jared5118 thing; if not, I know the phone number trick works (thats what I use on my WPA protected wireless). Also when you setup WPA you need to know if you used TKIP or AES; not sure the differences but you will need to specify if you manually make a connection.