The safest approach to this is to develop your own backup strategies and then follow thru on them...neither drive is "safer" as a HDD failure can occur at anytime and usually with little or no warning.
I use a few programs for this and although they aren't the only ones out there i have found thru experience they are the best for mu needs.
My main backup program is Acronis True Image. About 50 bucks U.S. it has saved me many times.
When i did my latest re-build after installing XP Pro and SP2 and all updates i also installed FireFox, Thunderbird all my diagnostics software and Anti-virus programs.
I then created an image using Acronis and burned it to CD. This is known as my "virgin" backup and is 10 times faster to restore than it would be for a repair install or for that matter a clean install of XP. It has everything i need for the basics.
Next i do an Acronis image of my HDD every 2 weeks and also burn those images. I also save the current image in a hidden partition on another drive. Reason for this is image files do not like scanning; defragmenting and some of the other maintenence routines i normally perform.
For the Documents and Settings folder i use SyncBack once a week and store that archive on the hidden partition. It allows incremental file comparisons so i'm not backing up from scratch; just what has changed since it last ran
Any programs i DLoad and test if they meet my requirements for being part of my machine get copied into a folder i call ZIPS. This ensures i have originals and this is burned to CD weekly as well.
Worst case scenario i am restored back to full running status usually within an hour and no further away than 1 week at most.
Works for me...
patio.