Is your game patched to the latest version, and if you are running Win7 or Vista, do you have the game installed outside of Program Files. If the answer to the former is "no," patch the game. If the answer to the latter is "no," reinstall the game to C:\Games\Bethesda Softworks. If the answer to both is "no," reinstall the game first.
Also, I recommend you start using Oblivion Mod Manager - http://tesivpositive.animolious.com/index.php?page=obmm
OMOD Installation - http://tesivpositive.animolious.com/index.php?page=omod_installation
Intro to Modified Oblivion - http://tesivpositive.animolious.com/index.php?page=intro_to_mods
New Users Guide - http://tesivpositive.animolious.com/#starters_guide