Backing up files is one of the most important things to do, and while it should be easy (partly because it *is* so important) it's also one of the hardest things to do right, even after over 20 years of widespread personal computer use.
At the very least, my personal files (email; spreadsheet with my checkbook, etc.; address books; memos and notes; photos and music) need to be backed up and stored outside the computer, and preferably in two places, one away from home in case of disaster like fire or flood or a meteorite crashing through the roof (hopefully while I'm at the grocery store).
So far so good. This can be done drag-and-drop style in any operating system nowadays.
But if I want to back up my whole system (I use Linux, but this goes for Mac and Windows, too), I'm facing a whole different situation.
I have had to restore my system from scratch several times, and it is not only no fun, it takes three or four days--and I don't even have that complicated a system. Getting all the software back in, customizing and making it work again, and getting back to the relatively comfortable place I was before the big crash, can be a nightmare and I've been in tears doing it several times, out of frustration and anger.
To my knowledge there is not one single piece of all-purpose backup software that *really, truly* can promise to make things right again in case of a severe loss. There are some that come close, especially for Windows users.
I am at a loss to know why, after all this time, such a basic and vital task has not been made easy for all users. It could be done. Nobody has done it.
A good thing to do, if your schedule permits, is to allow some automated program (you can write a little script to do it easily, under Windows) to back up your personal stuff at least every night, either directly to CD or DVD, or to a file that you can then copy to removable media and keep in a safe place. Software can be replaced; your personal files can't. My whole life is on my hard drive, so I do back that personal stuff up.