On zoo tycoon dinosaur digs how come the dinosaurs eggs won't hatch?

I had the same problem, there was an error during the installation while installing animals5.ztd file. Download the recovered file (https://rapidshare.com/files/2723833276/animals5.ztd) and put it into ...\Microsoft Games\Zoo Tycoon\XPACK1 , then choose overwrite. Eggs should hatch again and mammoths etc. should stop disappearing.