Learn English – a good word for a lack of knowledge on a particular subject matter

I would like to know if there is a word for the above situation. Particularly, I would like a word that replaces "X" in the following sentence:

You are so computer-X.

If it has to, it could fit in the following sentence:

You are so X when it comes to computers.

I have words for both, but the first is not a very intellectual one. The word I have for the first sentence is "ignorant". I don't like that word in this context, though, because it is fairly common. I would like an uncommon word for the former sentence. For the latter sentence, I have the word "inerudite", if I am using it properly in that sentence (it would be nice to know if I am not). I can live with using the using the second word and the second sentence, but I would like to know, is there a better word than "ignorant" that will satisfy the grammatical conditions of the first sentence?