A kindly soul was good enough to inform me that the texture paths in nifskope can't be like this:
"c:\program files (x86)\steam\steamapps\common\fallout new vegas\data\textures\colddeckgiftshoptextures\gifts\lighter\lighterparts.dds"
They have to be like this:
"textures\colddeckgiftshoptextures\gifts\lighter\lighterparts.dds"
Now I have about 50 meshes that require their textures rerouting. Is there any way of doing this other than manually? Because changing each one by hand is going to take sooo long =[
