Network key and Key index question

I'm trying to connect to my MN-500 router from a notebook running an
internal 54g adapter under XP Home. The notebook wlan properties page
requires Network key and Key index settings. I'm sure I've got the Network
key correct, but am unsure of the Key index setting. What does this
correspond to on the MN-500? I'm pretty sure I've got this correct also, but
after I make the entries and reboot the system, all IE pages I try show
"server not found".

All help appreciated and thanks in advance.