I have two internal HD's, each with a size of 320GB. The first drive has several partitions, including OS (Win 7), Data for work, Data for myself, Downloads, Multimedia and finaly Games.
The second HD is only used to store my daily Images (with Acronis True Image) of the OS partition and the two data partitions. Besides that I use Goodsync Pro to sync data from the data partitions with a folder on this second HD (easier acces then with an image).

To make sure that this isn't the only failsafe, I sync all my backupdata from the second internal HD to a 500GB external HD (once a week). This external HD (USB connection) I can store in a fireresistant safe. It's not a 100% failsafe system, but it's pretty close.