To back up the data just copy the whole folder, C:\XY Family Tree, to somewhere safe. (This assumes you're keeping your data in that folder.)
You could export each family as XYXchange. This creates a zipped file containing all the content you can see when viewing that family on your screen using XY Family Tree on your PC. You can put that file somewhere safe or even email it to yourself or a friend. However, XYXchange works only on one family at a time.
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