you probably will need to run MCPR as well as the windows uninstall. If the windows uninstall does not work run MCPR it will clean up the old install.
reboot and run
and reinstall from your account.
The best version for win8 is 12.1 but I am unsure AT&T is supplying that version yet. There is a version 11.6 that is copmpatible but 12.1 has a more windows 8 look.