o sorry, i interpreted your question wrongly. apparently this question should go in the models seciton. you can do this though by converting it to an mdl in text format and find where it says the path. just rename it.
Hmm..., this is hard to explain. Anyway it's not just display a plain text, but display the text in hex too.
Well, this is not the best way, but since i don't have model editor tools, i often use this trick to change path of a model or change animation name.
Open .mdl file with hex editor, then some screwed up characters will appear. Between a bunch of those screwed up characters there are path and animation name. Then, I just edit those in hex.