One question is how to remove both once you have them on. There's no uninstall option for either to allow you to reinstall the Virtual PC first on the second attempt ahead of the XP mode.
There's no listing for either seen in the Programs+Features as well as not seeing an uninstall option in the Start>All Programs folder.
Another thing would be installing the Virtual PC a second time to overwrite the first in order to correct any problems seen with the first install. You would follow that following a full system restart which most forget to do in order to install the XP mode the second time. Again a full restart will be needed for the initial startup. Sometimes it takes a few reboots before it will suddenly start running.