We had a similar issue with our company and this what we have done. We purchased a computer with Win2000Pro and use it as a file server. We have the main drive (C:) that is strictly for the machine itself. "D:" is our data drive and "E:" is a 120gb harddrive in a removable rack. We have two 120bg drives that we rotate. During the morning and evening hours all the the changing and important files are copied over to the file server's "D:" and to then be backed up to the "E:" over night. As redundancy we have put removable racks on our "important" PCs. I ghost these once a week, shut the unit down and pull the hard drive out so that it cannot be changed by accident or via a virus infestation. This has worked for us. An additional bonus too we can store the removable harddrives off site if we choose.
Here's how this saved our data - one of our digital medical records directories was accidentaly erased. The second harddrive was backed up (ghosted) the night before so the scanned documents from that day was all that needed to be rescanned once the ghosted drive was copied back over the one with the erased directory and goofed up indexing because of it. Our down time, 1 1/2 hours - and there was no big issue about it. We run Win2kPro and Win98SE platforms. Hope this helps you.