Customize installation, cannot change parameters

I have 3 servers (N1, N2 and N3). N1 and N2 both have Nav server, client and administration tool installed. Server N3 has only the client installed which connects to an instance on N1.

I want to customize the installation on N3, on N3 I want to add the server and administration tool.

When I run setup, choose "add or remove components", add "administration tool" and "Server" the next screen "specify parameters" appears. However, on this screen I cannot change the parameters I want to change, for instance the server name should be changed from N1 to N3 but I am not able to do so.

It seems the settings I entered for the client to connect to an instance are somehow fixed ..????
I can not imagine I should uninstall the client first and do a reinstall of all components I would like to have ..???