You can just cast the setting back into a List. I usually add a helper function to read settings, to prevent reading something that isn't saved:
private static object readSetting(string key)
{
return IsolatedStorageSettings.ApplicationSettings.Contains(key) ? IsolatedStorageSettings.ApplicationSettings[key] : null;
}
You could use that function to restore your List, for example like this:
List<String> projectList = readSetting("yo") != null ? (List<String>)readSetting("yo") : new List<String>();