If you are running the game installer from the disc, it is not supported on 64-bit versions of Windows.
x64 does not support 16-bit applications, the Rebellion game installer is a 16-bit application, however, the game itself is a 32-bit application.
x86 (32-bit) versions of Vista and Windows 7 can however still run 16-bit applications such as the native installer.
There is an x64 installer thread in the main forum. You can find my post here documenting how to manually install the game onto x64 Vista,7 systems.viewtopic.php?p=67704#p67704