Mounting an extra internal hard drive typically requires manual effort by the superuser, but there is a way to configure it to be done (rather easily) at boot time through a handy utility called pysdm.
The first thing you want to do is install pysdm from either synaptic or the command line. The command-line way is:
sudo apt-get install pysdm
Now that pysdm is installed, you’ll find it under System > Administration > Storage Device Manager
Starting it, you’ll see your list of drives on the left pane. Select the drive and partition you want (this assumes you know how to do that already) and click Assistant.
In assistant choose at least The file system is mounted at boot time along with any other options you might want.
Apply and reboot to verify it’s working.