For example in the following label I want to use SmallCaps, but they only show up on Windows 8 and higher. On Windows 7, there are just normal letters.
<Label x:Name="servername" Typography.Capitals="SmallCaps" Content="Server xy" VerticalAlignment="Bottom" FontSize="15" Margin="10,0,10,31" Padding="5,0" FontWeight="Light" Height="19" HorizontalAlignment="Left" SizeChanged="servername_SizeChanged"/>
I'm using .NET Framework 4.5 and the font is Segoe UI Medium (and in some other labels Segoe UI Light), which is installed on both systems.