'The oblivion launcher could not find the oblivion game executable' appears when choosing play from the autorun menu or clicking on the game shortcut.
Reinstalling the game will remedy this issue. Saved data is stored My Documents\My Games folder so no progress will be lost if you choose not to delete saved games. When reinstalling the game, exit the autorun window if it appears
Double click 'My Computer'
Right click on the CD drive containing the Oblivion disc
Run Setup from the disc contents that will appear