Your notebook computer's disc eject mechanism is electrical instead of mechanical. To insert a disc, you will need to push the disc in more than 85% of the way into drive before the optical drive will register the disc and pull it the rest of the way in. This is normal behavior and is done in order to protect the drive from accidental damage.
To eject an optical disc at startup, if the disc contains system software, press the mouse button while the computer starts up until the computer ejects the disc. If the disc does not contain system software, wait for your computer to start up completely and drag the disc icon to the Trash or use any of the other accepted methods to eject the disc.
Note: Because the drive is slot loading, you should insert only round 120mm discs. The drive does not work with irregularly shaped discs, which could damage the drive if inserted.