How to remove a duplicate mirror?

I just downloaded a 3D model and when I imported it to use it, it came with a mirror duplicate. I can’t edit the mirror directly but when I make changes to the original model, it changes the mirror as well. How can I get rid of the mirror?

I’m not sure what you mean when you say you can’t edit the mirror directly, so here are a couple of guesses:

  1. If you mean that it’s actually part of original object and the vertices occupy the same spaces as the original vertices…
    Select the object, go into Edit Mode and find the Remove Doubles button in the Tool Window. And, of course, click that button.

  2. If you mean that it’s a separate object and for some reason you can’t select it, edit it or whatever…
    Post your .blend file. We’s gonna have to look at it.