SUCCESS!!!
The only thing today to put a smile on my face is...
Getting Limes to work!
I was looking at the Librarians profile in the Management Console, and there was one of the boxes I've never used, 'Legacy programs enabled'.
You know when something smacks you in the face (yeah, you all shout, smack the newbie!), and you think "that can't be it, can it?". It was.
I forgot the software is so old it wasn't designed for XP (we currently run it on Me).
I've set the permissions to allow everything for the user on the drive, so I'll start tightening them down to an acceptable limit, then I'll pass the PC ready to use.
Now then, back to setting up our VLE.
Thanks everyone for the help and ideas, if I hadn't come here then I wouldn't have had the heart to go back to working on the software.