Thanks for the advice. I'll remove all the modules and then upload a simple one. I'll check the permissions as suggested. I'll let you know what happens...
Thanks again for the advice.

My Xoops 2.0.18 site seems to be working fine. It's the first time I've ever done it. I have uploaded a few menu navigation modules (to see which one I liked, then uninstall the others). These are the first modules I have tried to install. But they're not appearing in the System Admin menu, so Xoom isn't seeing them. I checked the file structures on the site and they seem OK to me. What else could be wrong?

Please help, as I was just starting to like Xoom.
Thank you.