Hey Beth,
Welcome to Ironworks.
unfortunatly Undermountain as well as most online Mods require the original game plus Shadows of Urentide & hordes of the Underdark.
To see what servers you can connect to you can select your multiplayer button on your NWN splash screen, connect to gamespy and it will bring up a list of servers that currently have games on them. All you need to do is then find one with your packs on them.
Hordes of the Underdark is still available as a stand alone expansion (I've still seen it in the shops) however with the platinum pack being released the chances of getting Hordes by itself is getting slimmer and slimmer.
My advice. Get HoTu if you want to play online. Most servers will need it.
Cheers!
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