This is a 52-week extension to a study to assess the safety and effectiveness of vildagliptin, an unapproved drug, compared to metformin in lowering overall blood glucose levels in people with type 2 diabetes who have not been previously treated with drug therapy to lower their blood sugar. The purpose of the extension study is to gather data on the long-term safety and effectiveness of vildagliptin in people with type 2 diabetes.