A second HDD is fast and reliable, but will not help you if your computer gets stolen, or your house burns down.
I have a Seagate Travan, with 2 sets of 4x20 GB tapes - A and B. It does an incrememntal backup overnight, and every week, I change the tape set, and put the other in the car.
I have a USB one, so I can use it on my laptop if I need to (another plus over a second HDD). But an internal one is faster.
So far, I have not had to restore - but I am paranoid like you. With backups, I think this is a GOOD thing to be.
