By default, xaml makes the checkbox invalid. Change <Checkbox /> to <CheckBox></CheckBox> and add a text block inside the tag to add content. Add padding to change field alignment.
<CheckBox x:Name="ChkExcel" Grid.Column="0" Grid.Row="3" Margin="0 3 0 3"> <TextBlock Padding="10 2 0 0">Microsoft Office Excel</TextBlock> </CheckBox>
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