I use the winXP Pro back-up application (I think it is a version of veritas) to back up all the necessary data from several workstations to a mirrored 200gb array. I also back up the contents of the i-bays at the same time. I find it just as fast to do a complete back up with replacement as to do an incremental or differential. It makes restoring much easier as well. I use the sme back up to tape to back up the settings and configuration of the sme box to tape once a week with a change of tape following the event.
This is on a simple network of 11 workstations, a dedicated file storage unit, a dedicated back-up unit, and the sme unit. On commercial networks, the back-up routine is different, depending on the data needing to be archived and the resources of the network.