I'm definitely getting tired of debugging other companies installers. The Overloud guys are good guys, but their install directory sprawl (we'll stick things all over the place) and lack of attention to details is disappointing.
Just in case anyone wants to know, the way I worked this is out was by running Microsoft's SysInternals Procmon tool while using the installer. It records a log of every disc and registry access. I then combed though the logs and saw what it accessed. This is how I knew it looked at the %appdata% directory and then stopped installing TH3 components.