[FFL]

OK, so the Home Folder on the Desktop is there whether or not the LaCie is plugged in - sorry, I wasn't getting that before.

What happens when you open the Desktop folder in your Home folder - does the Home folder appear there? With all its contents?

It will either require netinfo tinkering (which I'm not the most expert in), or VOX' suggestion of creating a new user. You might have to copy your Home folder contents into Shared, in order to get them into the new user.