Jill Warrior of the Universe Keeper of the Disk

Jill is an eleven year old girl who finds a spaceship in her back yard. she encounters the alien of the ship and fights with him and won. The next day she finds a cave with an ancient computer and five disks. On the disk is the history of the earth and the reason the aliens want the disk. Jill must protect the disk and keep them from the alien or the earth will be at war.