Recommendation for a desktop backup solution

Hello,

I am looking for a recommendation for backup software for Windows
XP Pro desktops. I need to back up files from four different systems
to an Iomega StorCenter device but I am not sure what PC program I
should use to back things up.

We’ve tried Second Copy 7 by Centered Systems but there is a
problem with that software in that it will not backup files that are in
use. The office is very eco-friendly and they do not want to leave the
machines on during the evening to backup so I am not sure what
software to suggest for them.

What do you recommend and WHY do you recommend one product
over another?

Thanks,
Marcel