Open your File Explorer (for Windows), then go to Documents > My Games > Oblivion, delete Oblivion.ini, Launch the game again, and it will generate a new Oblivion.ini witch should fix any broken configurations. However in my experience, one of my mods keeps breaking Oblivion.ini again. I think the best way to circumvent this is to make Oblivion.ini read only. You won't be able to configure things like the video or sound settings (through the Oblivion launcher or in game) as the file is set to read only and oblivion cant write to Oblivion.ini. To do this, acssess your Oblivion.ini go to properties, then tick the box that says "Read only" Hope this helps.
