Oblivion: The Shivering Isles: update problem?

I am having trouble with updating my (legal) copy of The Elder Scrolls IV: Oblivion: The Shivering Isles to version 1.2.0416. When the update is trying to update the "Readme.txt" file in the Oblivion directory, I get an error message that says, "Old File not found. However, a file of the same name was found. No update done since file contents do not match." If it might make a difference, my copy of Oblivion and Oblivion: The Shivering Isles are part of the "Game of the Year" compilation edition. I realize that this is 2010 (and that this game is from 2006), but I am a compulsive updater and this has bugged me for years. Any help whatsoever is greatly apperciated! Thanks in advance.