What version of Creo (1 or 2)?
Can you attach an example file here?
2013 will open Creo v1
2014 will open Creo v2
Not sure if there is an update for 2013 to allow opening of Creo v2.
If you don't have Inventor 2014 you might download a trial or see if you can get a trial of Fusion 360.
Access a broad range of knowledge to help get the most out of your products and services.