Here is two tools to http://tesivpositive.animolious.com/?page=programs_and_utilities mods.
I believe the tes4files is the one that you should use, but the Oblivion Mod Remover may also work.
If that doesn't work you could head over to the http://www.gamesas.com/index.php?/topic/1099204-relz-oscuros-oblivion-overhaul-133/ thread to read about the uninstall instructions. :read: