I think your folder structure is wrong. It should look like this: but it looks like this: I still got a CTD when loading, but it worked fine when I changed the follwowing things (not all of them caused a crash, some just an error message). - Delete test_CIV4LeaderHeadInfos2.xml to make sure it isn't loaded. - Make sure that all ArtDefines references are to existing art files (I changed some from upper case to lower case). - Change the art (EarlyArtDefineTag) of your UNIT_WAMPANOAG_GUERILLAS from ART_DEF_UNIT_HELLEBARDIER to ART_DEF_UNIT_WAMPANOAG_GUERILLA. This stopped the game from crashing. Remember: whenever the game crashes without warning, it's usually the art files that are to blame (references to non-existing art). I still got some error message though: - In your Civ4CivilizationInfos.xml, the following code bits are missing: -- an end tag </Cities> after line 42. -- you need a tag <Leaders> right before the first <Leader> tag and a </Leaders> tag after the last </Leader> tag. This is necessary to allow for multiple leaders. - Your unit is called UNIT_WAMPANOAG_GUERILLA in your CivilizationInfos, but UNIT_WAMPANOAG_GUERILLAS in your UnitInfos. After making these changes (dunno if the first two are necessary, the last three definitely are), it worked fine.