You can open the AppXRuntime.adml file in a good editing program such as Notepad++ and see where the XML has an error. There is a duplicate of the AppXRuntimeBlockFileElevationExplanation keys. This is not due to corruption, and is not a major error. It just looks like during the last build a team was working on Group Policy and had unfinished work and forgot a duplicate in there. I wouldn't recommend copying the files from Win8, I would recommend backing up the adlm file and removing the duplicate key entry. If I have time later today I will make a video of just that.