In complete chronological order: We uninstalled Total Defense, rebooted, attempted to install ESET, failed with the aforementioned error, tried to remove all traces of ESET in both the registry and any folders or files in safe mode, attempted a reinstall, failed, utilized the ESET Uninstaller in safe mode which found remenants of Symantec, attempted to install again which failed, tried to use the ESET uninstaller again which uncovered nothing, and any attempts to install after have been met with the same error message.
Apart from wiping the slate clean and just opting for a format and install, I'm spinning my tires in the mud trying to get this to work.