All additions of Windows 2000 and XP include a backup program; installed by default.

Look under start\programs\accessories\system tools\
and you will see backup.

You can schedule it to run at off hours.

I back up to a searate physical disk nightly; and burn "My Documents" (where I keep all my stuff) to CD every few weeks. I keep the CD at the office; I have insurance for stuff in my home; but that CD has all my records -- all old emails; financial records, digital family photos etc.

And for those that asked -- you can script powerquest to attomate it. (At least the DOS mode version works; they have a new ver that I haven't seen yet that supposedly even runs under Windows).