Although the option is available in the game, Bethesda is advising Xbox 360 Doom 3 BFG edition players not to install it to their consoles’ hard drives.
“There is no performance advantage to installing the game to your hard drive,” admitted Bethesda’s global community lead Matt Grandstaf.
Even more, installing the game to the Xbox 360 hard drive actually disables some features. More precisely, doing so prevents the classic Doom and Doom 2 games bundled on the disc from running.
So why did id Software include that option which wastes hard disk space while reducing functionality and offering no benefits whatsoever? Our guess is as good as yours. Just don’t use it.