It's easy. Find this file
C:\Program Files\Firaxis Games\Sid Meier's Civilization 4\Beyond the Sword\Mods\Next War\Assets\XML\Civilizations/CivilizationInfos.xml
Open it with Word Pad or Note Pad.
Find this
<Type>CIVILIZATION_AMERICA_INC</Type>
<Description>TXT_KEY_CIV_AMERICA_INC_DESC</Description>
<ShortDescription>TXT_KEY_CIV_AMERICA_INC_SHORT_DESC</ShortDescription>
<Adjective>TXT_KEY_CIV_AMERICA_INC_ADJECTIVE</Adjective>
<Civilopedia>TXT_KEY_CIV_AMERICA_INC_PEDIA</Civilopedia>
<DefaultPlayerColor>PLAYERCOLOR_BLUE</DefaultPlayerColor>
<ArtDefineTag>ART_DEF_CIVILIZATION_AMERICA_INC</ArtDefineTag>
<ArtStyleType>ARTSTYLE_EUROPEAN</ArtStyleType>
<UnitArtStyleType>UNIT_ARTSTYLE_EUROPEAN</UnitArtStyleType>
<bPlayable>1</bPlayable>
<bAIPlayable>1</bAIPlayable>
<Cities>...
Change it to this.
<Type>CIVILIZATION_AMERICA_INC</Type>
<Description>TXT_KEY_CIV_AMERICA_INC_DESC</Description>
<ShortDescription>TXT_KEY_CIV_AMERICA_INC_SHORT_DESC</ShortDescription>
<Adjective>TXT_KEY_CIV_AMERICA_INC_ADJECTIVE</Adjective>
<Civilopedia>TXT_KEY_CIV_AMERICA_INC_PEDIA</Civilopedia>
<DefaultPlayerColor>PLAYERCOLOR_BLUE</DefaultPlayerColor>
<ArtDefineTag>ART_DEF_CIVILIZATION_AMERICA_INC</ArtDefineTag>
<ArtStyleType>ARTSTYLE_EUROPEAN</ArtStyleType>
<UnitArtStyleType>UNIT_ARTSTYLE_EUROPEAN</UnitArtStyleType>
<bPlayable>0</bPlayable>
<bAIPlayable>0</bAIPlayable>
<Cities>...
Do the same thing for the other civs you don't want. You can either do this in your regular Next War, or copy and paste the whole folder as NextWar2, so you have both versions. As if you couldn't easily go in and put something this simple back. If you have Vista you have to make the change somewhere else and paste the changed file in and give Vista permission because by default it won't let you change things in the Programs directory, though it will let you add and replace things.
for X-mas, and have greatly enjoyed it. I would like to play the Next War mod in the regular game, but I don't want to have, say, the Pan-Asiatic People whatever as an AI, and I like having random AI's, not choosing them in custom. Is there a way to get rid of the Next War civs without modding, which I can't do at all?
Thanks for the help! 
I had no idea what to change with the filenames, etc. so this was really helpful. I haven't played it yet, but I checked the Civ Chooser screen, and it has no Next War civs.
