It seems that Doom 3 BFG Edition is having some troubles if installed to the Xbox 360 hard drive. Users have reported to Joystiq that upon installing the game to their HDDs, Doom 1 and 2 can not be accessed from within the game’s menu screen. Bethesda’s response to the odd error is posted below.
“Doom 1 and 2 are the same games that are currently available on Xbox Live. Installing Doom BFG files to the system’s hard drive could cause a conflict with the existing XBLA game files,” a Bethesda spokesperson told Joystiq. “Players should not see a performance advantage by installing Doom 3, so we recommend not installing the game to the Xbox HDD.”
The publisher advises users who installed the BFG Edition to go to “My Games” on the Xbox Dashboard, to access the two classic games.
[Source]