Aroth if you reinstalled from scratch and still getting oddities then something is screwed elsewhere.
It sounds like you aren't running the OFF Manager properly, or you didn't clean out the old problem one completely first.
http://www.overflandersfields.com/FAQ.htm#A21
See from "If you have other odd errors:"
Check your drive for errors, right click on a the drive in My Computer, Properties, Tools, Check now.
Make sure you run OFF Manager from the new shortcut
>>"This time, it wanted the OFF Disc back in the drive as well as the CFS disc."
What does that mean?? When you install OFF it will run, find CFS3 install if you have it, then carry on. It will not want the disk back in if the install has completely finished. Make sure you don't take the disk out early it takes a while to install and unpack.