I just downloaded it and looked at the textures...

.dif are for diffuse
.alpha are for transparency
.spec are for specular reflection
.ddn are tangent space normal maps

there is an nvidia photoshop plugin to read and write dds files and it can be found here https://developer.nvidia.com/nvidia-t...dobe-photoshop.

However, this files seem to have already been converted.

Here is a short tutorial on the nvidia normal mapper filter ... Creating Normal Maps In Photoshop - YouTube