Can you post you /etc/fstab here?
You will need to add a line to this file to point to your new drive.
I suggest mounting the drive under your home directory, for example /home/<userName>/data. Create this directory, and then add the following line to fstab using your favourite text editor:
/dev/hdb1 /home/<userName>/data ext3 defaults 0 2
Obviously, replace /dev/hdb1 with whatever your new drive is, and <userName> with your username.
I hope this helps