[iBook] Samba networking questions

[Fearsome Orange]

Hi all,

I have a mixed network (two Windows machines and this here iBook).  I
have turned on Windows sharing on the iBook, and while I can see it
from the WinXP machine, I cannot connect.  When I connect I get a
window that asks for my password, and the username is:  
ip.address.of.ibook\Guest
which I cannot change (it's 'greyed out').

Could someone point me in the right direction?  The only two passwords
that I use (root, and the one user I have) do not work.

What simple thing am I missing?

Thanks in advance.

Jean-Paul

(PS, before anyone starts on me about windows sharing over a network,
I AM behind a router)