missing .lui file?

hi, my name is Chris and i'm from Holland. I have a few questions about the themes because i don't understand anything of this. (I'm not so good in English...) firts of all, what is DX 2? and how can i get this? i read it all over the pages but i don't understand. I understand i need this but does it also helps me with this problem? When i want to install a theme than a error appears. It sais that there's a file missing called ''.lui'' What can i do about this? please help me

thnx in advance