Setup Swtiches - network based notes.ini

I have a client who has all their users using the Notes.ini based on the network. They wish to run an upgrade to 6.51, however when they run the setup it treats the setup as a new install, it doesn´t pick up the network based notes.ini Is there a switch to point to a different ini file (eg h:\notesini\notes.ini) or a way of running a silent install pointing to a different ini file?