Trouble generating a valid WEP key on an xp computer and Linksys router

On the Linksys Router setup page, I used a passphrase to generate a 10
digit (64 bit) key. Four such keys are generated (Key #1 - Key #4).
Yet, in xp's Wireless Network Properties window (for the wireless
adapter of that, the 2nd and last, computer), there's only space for 1
key. I tried the first one (Key #1) and it didn't work. Also, there's
no "Key Format" and "Key Length" fields in that window (Wireless
Network Properties), as the Linksys User's Guide shows. What am
I missing?

Al