http://www.hydrofarm.com/product.php?itemid=3175
If it's that ballast you can't just swap cords. You will ruin the ballast in doing so. Best to either connect it to a 240v or get a new ballast.
*Word of caution to all would be posters. Unless you know EXACTLY what you're talking about, you might want to think twice about replying. Had he or if he actually swaps plugs and blows his ballast up who knows what might happen, he could end up burning his house down. All because of some misinformation given on this forum. Be wise with what you're talking about. If you don't know, don't reply just to up your rep.
The misinformation I'm seeing on this forum now days is frightening.