Ok, thanks Francesco. I have looked at the developer documentation for OpenERP 7 but it seems to assume a lot of prior knowledge. Can you recommend a resource (a tutorial perhaps) that walks a person through the process of creating a simple module?

A bet way to develope a module is to follow the documentation and read the code of "idea" module. A simple module, in addons, used as example for benniger user.

Right, I will have a look at that. In the meantime, someone may find it of interest that after backing up and updating to the latest nightly build, all of the custom fields that I had created in the Employee form were still there. I can only assume that whatever information was stored when I created the new custom fields was not overwritten when I did the update.