1. Take the game out! It's the safest solution.
2. Go into X3 config live and select X3 config live - Customize X3 BIOS - Disabled CDRom Boot = Enabled.
But BE AWARE that if you disable DC/DVD booting you will no longer be able to boot rescue discs if anything goes wrong....... It shouldn't be a problem with the X3 because you should always be able to get back into X3 config live to set it back to Disabled again, and you can always boot with a different BIOS (e.g. X2.5035) on another bank.