If you’re planning to play Doom 3 BFG Edition on your Xbox 360, and typically install your games to the system’s hard drive, you might want to reconsider that if you plan to play Doom and Doom II.
According to a report on Joystiq, the copies of Doom and Doom II that are included for free with Doom 3 BGF Edition are basically the XBLA versions of the game. So, installing those games to your drive could cause conflicts for players who already purchased the XBLA versions of the games.
Because of that, installing Doom 3 BFG to an Xbox 360 HDD specifically blocks access to the older Doom games from inside its menu.
“Players should not see a performance advantage by installing Doom 3,” a Bethesda spokesperson said to Joystiq, “so we recommend not installing the game to the Xbox HDD.”
However: If you do want to install the game, you can still access the two older Doom titles—they’ll just only be accessible via the Xbox 360 Dashboard under your “My Games” section.