Silverlight grid col question

[Sems]

Hi

I cant' find a good WPF/Silverlight group, does anyone know of one? I
thought I'd try my question anyway though.

I've got a grid that I want to stretch 100% across the screen of a
Windows Phone 7. I though that using width = auto and width = * would
of done this but its not. Instead the grid is only covering about half
of the screen. Can anyone please help me with this, this is what my
XAML looks like...

<StackPanel x:Name="singles" d:LayoutOverrides="Height">

<ListBox ItemsSource="{Binding
CurrentlySelectedSingle}">

<Grid>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>

<TextBlock Grid.Column="0" Text="{Binding
CurrentlySelectedSingle.Artist}" Margin="0" Style="{StaticResource
PhoneTextSubtleStyle}" VerticalAlignment="Bottom"
d:LayoutOverrides="Width"/>
<TextBlock Grid.Column="0" Text="{Binding
CurrentlySelectedSingle.Name}" Margin="0" Style="{StaticResource
PhoneTextSubtleStyle}" VerticalAlignment="Top"
d:LayoutOverrides="Width" Grid.Row="1"/>
<Button HorizontalAlignment="Right"
Foreground="{StaticResource GoldHeadingBrush}" BorderThickness="1"
BorderBrush="DarkGray" Content="Buy All" Grid.Column="1"
Grid.RowSpan="2" x:Name="btnBuyAllTracks" />

</Grid>
</ListBox>
</StackPanel>