How do I map a network drive from a boot disk with no username/password prompt??

I am trying to get a client to PXE boot, get served an image of a boot
floppy by RIS modified with Emboot RISME which then runs a batch file
menu. This menu offers a choice of Ghost images of different
combinations of windows and office versions. All this works fine but to
make it as simple as possible for the end user I want to remove all the
authentication steps apart from the final logon once the correct
version of Windows boots. I have automated the RIS logon by amending
the login.osc file however I can't seem to do the same with the
username/password request when the ghost boot disk maps a network share
(Please enter your username or press ENTER if it is ADMINISTRATOR). PC
DOS net use comaand doesn't allow me to specify a user and password...
I don't need it to be secure as it is a testing environment so I don't
mind typing the password into a boot file. Please help - this is really
starting to wind me up!
Thanks in advance.