When using MS tool, remove JUST the Comodo entry of the Add/Remove programs list.
There isn't one, that's the problem. Comodo seems to be completely uninstalled from my system. Some leftovers from previous installation must be doing the damage (I know Comodo used a crappy installer in the past, that is changed in the newer versions),
Delete the following Registry keys (if you want, make a backup first, for safety, better safe than sorry).
HKEY_LOCAL_MACHINE\SYSTEM\Software\Comodo
HKEY_LOCAL_MACHINE\SOFTWARE\ComodoGroup
HKEY_CURRENT_USER\Software\ComodoGroup
Try again...