preventing file deletion

Sure. How it is done depends on the machine. I assume it is some sort of PC, so for Windows98, you use System Policies and the Policy editor.

Here's a nice tutorial for that.
http://www.zisman.ca/poledit/
(remove any spaces from the url)

ForWindows2000/NT, the admin would configure the users' profiles appropriately with the desired permissions.

HTH
Nikki

Exactly how you go about this will of course depend on your security setup, etc...

You should be able to go under your security settings and select "Special" file or folder access. Then remove the check from the delete option. Grant only the permissions you want them to have.

Bear in mind though, if they cannot delete files, you will be called upon to remove old data, fix files that were modified incorrectly, etc...so it's a bit of a double edged sword. We just make sure we backup daily and restore the files as needed. Education of your users may be a better solution...and will cause less frustration all round in future. Plus, you'll avoid some confrontational "Well....until YOU changed things I could do X without any problem..."