So the problem is that you can save them, but you're unable to retrieve them?
If this is the case, an XmlDocument object has a
LoadXml method that you can use. You supply the source XML as a string (which you would read from the file you saved) and it loads the XML into the XmlDocument object that calls it. Make sure you call it from within a try/catch block as if there are any exceptions, you'll want to be able to report the errors.
Now you'll have an XmlDocument object that's the same as the one you wrote. Just process it to get the nodes containing the names of the items you want checked, then find them in your listbox and check them.