A few weeks ago my Macbookpro was acting up, after the kids were playing with the Photobooth app. and others....
Kids do the darnedest things - "Art L"
So I did a re-boot

It would not restart.....
So I booted from the install disk, ran "Disc Tools" and could NOT repair the drive

So I erased the drive and ran the "Time machine" back-up app.
Nothing to lose
It did not take very long and almost everything was back including all the pref.
The good, nothing in itunes was lost.
All my movies were on the back-up drive.
The bad, the iPhoto Library WAS lost, (not backed-up?) I had all but a few events saved on other drives, but still hate to lose even a few memories.
I lost the Route 66 street nav app. but it saved my routes?????? just re-installed.
I lost the NG Topo maps app. but still have all the disc image data files?????

Anyway, I'm glad I took the time to add a back-up drive. (very affordable insurance)
Now I know the weak spots in my conf. of the "Time machine" app.
I'll be better prepared for the next time