<Window.Resources>

        <Style TargetType="Button">

            <Setter Property="Template">

                <Setter.Value>

                    <ControlTemplate TargetType="Button">

                        <Border Name="RootElement">

                            <Border.Background>

                                <SolidColorBrush x:Name="BorderBrush" Color="Black"/>

                            </Border.Background>

                            <Grid Margin="4" Background="{TemplateBinding Background}">

                                <ContentPresenter

                                    HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" 

                                    VerticalAlignment="{TemplateBinding VerticalContentAlignment}"

                                    Margin="4,5,4,4" />

                            </Grid>

                        </Border>