If you talk about a computer nerd you can use the English because there isn't really any translation. However this word isn't very known and you would be better understood by using the English word "geek" that can have a positive or negative meaning depending on the context. In a general context you can maybe use the word "intello" that come from "intelligent". As for "geek" this word can be derogatory or positive. Maybe you should give us a complete sentence in French or in English because we can't really give you the correct translation without context.