The office files are, in fact, backed up on another hard drive regularly. One can never be too sure.
Any other suggestions, anyone? I'm thinking about formatting entire HD and upgrading to Panther (non-server edition), but I am still wary of Panther due to its share of problems.

It could be a deleted file that is still being held open by a process.

Now I have not tested this on HFS+, but on all other unixes I have dealt with, if you open a file and write 100MB to it, du and df will both see that space taken up.

If a process opens the file (for read or write) and then you delete the file, the 'directory entry' goes away but the file still has a 'link' count of 1 due to the reading process, so the space is not freed. Once the process quits, the link count drops to 0 and the OS will turf the file.

In such cases, while the process is still holding the file open, 'df' should report the correct amount of used disk space, but du will not as it checks files that have directory entries.

You may want to try a reboot and see if you then have recovered your space (I think it may be too hard to locate and kill a process that is doing this, but that would be the better option).

I have seen questions on deleting swap files (/var/vm/swapfile0,1...), and would think this would apply to them as well.

As I said, I have not had a chance to test this on HFS+, maybe someone with some more time on their hands can do it.....

The swapfile0 located in /var/vm is just 87 mb. There is but one swapfile in that directory. Thank you for your advice.

The swapfile thing was just an example. It could be any file that is held open.

Have you tried a reboot?

For future reference: RAID (in pictures).

I don't think it's applicable to the situation under discussion here, though.

I have rebooted quite a few times now, for various reasons. And to what avail? None noticeable. I don't understand why it cannot list what is eating my space.

Well, it may take a while, but could you post the output from the following commands?
(I know we have seen the df before, but things may have changed.)

The other thing that is a possibility is the mounting of a file system onto a directory that already contains stuff. When that happens, du cannot see the files contained in the directory as they are 'covered' by the new mount, but df still knows about them.

Any mounted filesystems?

I'm at home right now. I just wanted to say gracias for all of your altruism. I'll try that command tomorrow when I'm at the office.

Merci

Miss Virgil