If the Aero theme is causing my problem, isn't there a way I can use a simple template for my column headers that won't be affected by the OS theme?  How come the xamDataGrid can't control the way it's displaying the headers?  My software has to work with the Aero theme, or the classic theme, and use all the available horizontal space possible.

Fine. You found the cause of the bug. Now, how do I make the xamDatagrid work with the Aero theme now?  Like I said before, I need to set my columns width precisely: horizontal space is limited.  

Is it possible to make the grid not be affected by the Windows theme?  Can't I control the way things are displayed in WPF?

Your Win7 columns are wider than in XP...   Did you set the field widths?  I need to have the exact same width on all platforms.

I'm using version 9.2.  Here is the code I used to test:

From a new project:

<Window x:Class="WpfApplication1.Window1"

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    Title="Window1" Height="300" Width="655" xmlns:igDP="http://infragistics.com/DataPresenter">

    <Grid>

    <igDP:XamDataGrid Name="xamDataGrid1" VerticalAlignment="Top" DataSource="{Binding}">

      <igDP:XamDataGrid.FieldLayouts>

      <igDP:FieldLayout>

        <igDP:FieldLayout.Fields>

          <igDP:Field Name="Id" Label="Very long label to say Id" Width="130"/>

          <igDP:Field Name="Name" Label="This is another long label for the name" Width="200"/>

          <igDP:Field Name="BirthDate" Label="Not so long for the BirthDate" Width="150"/>

          <igDP:Field Name="Comment" Label="Any comment?" Width="80"/>

        </igDP:FieldLayout.Fields>

      </igDP:FieldLayout>

        </igDP:XamDataGrid.FieldLayouts>

    </igDP:XamDataGrid>                                            

  </Grid>

</Window>

namespace WpfApplication1

{

  public partial class Window1 : Window

  {

    public Window1()

    {

      InitializeComponent();

      PersonList = new BindingList<Person>();

      Person p = new Person();

      p.Id = 1;

      p.Name = "Fred";

      p.BirthDate = new DateTime(1977, 01, 01);

      PersonList.Add(p);

      this.DataContext = PersonList;

    }

    public BindingList<Person> PersonList { get; set; }

  }

  public class Person

  {

    public int Id { get; set; }

    public string Name { get; set; }

    public DateTime BirthDate { get; set; }

    public string Comment { get; set; }

  }

}