[quote="Dave_Noonan, post:6, topic:308188"]
As others have indicated, I would also strongly suggest talking to a priest.
If your former spouse is still living, you will likely need an annulment of your first marriage. Your case will also depend on whether any of the involved parties are/were baptized and whether your first spouse had any previous marriages prior to your marriage to her and the circumstances of that marriage. Generally, the Catholic Church assumes marriages are valid (civil or otherwise) unless they can be shown to be otherwise.
First off: Yep... get ye to a priest!
Second off: the "you will likely need an annulment" isn't necessarily true (if by "not believers", you mean that neither of you were baptized Christians at the time of the marriage or during the marriage). However, when you go to talk to the priest, have as much information (as possible) ready: for you and your wife, all of both of your ex's, and all of their ex's, you'll want to try to know what their Christian status is (that is, are they baptized Catholic? if not, are they baptized Christian? if so, in what denomination? if baptized, on what date (and where)?). In addition, knowing the dates and places of any marriages and divorces is relevant.
Your priest will know what other information (if any) is relevant. Going to him with a solid grasp of the facts is helpful, though...