I downloaded the english instaler, but the game is in spanish, Why is that happening? Does it have something to do with the fact that the main language of my computer is spanish? Is there some way to fix it? I don't want to play videogames in my mother language, I am used to play videogames in english and I like them that way.

According to the dev:

I guess I can wait for a patch, I preffer not to tamper with that kind of thing, the voices are still in english anyway.
Well, Mcrosoft proved why it has bad reputation again.

You can safely try, if something doesn't work afterwards, simply re-install the game.
Instead of renaming you can also delete DustAET.resources.dll in this folder \Dust - An Elysian Tail\es\

ill give it a shot

I did not get what you mean by renaming the .dll file, so I deleted it for my OS language, and now the game is in english, thanks a million.