This depends on the .NET version (please update the tag for reference). In .NET 4.5, you have a property IsXAxisQuantitative on the Series that you can set to 'true' to prevent this behavior:
Chart1.Series[0]["IsXAxisQuantitive"] = true;
or
Chart1.Series[0].CustomProperties = "IsXAxisQuantitative=True";
In older versions of .NET, you could add a transparant dummy point at x != 0:
DataPoint dummyPoint = new DataPoint(1, 0);
dummyPoint.Color = Color.Transparent;
Chart1.Series[0].Points.Add(dummyPoint);