you can do this with telnet
I've tried telnet on Win2K (sorry, pretty out of date...) so it may work similarly on XP or Vista. Just be sure to set
NTLM = 0 under the settings. See this link:
http://www.netadmintools.com/art246.html
here's the caveat - telnetting to a windows box from a *nix box doesn't always work well (I've noticed this primarily when I change the server port from 23 to something else, like 923). You may find that the 'return' key doesn't seem to work, and your typing may come through in chunks. This is because of a mis-matched mode control negotiation during the connection setup (yes, telnet negotiates a lot of control functionality under the hood, largely unknown to the end user).
I won't go into the details here, but I've managed to make this work by using a local .telnetrc file in my home directory:
~# cat .telnetrc
newt mode character
where 'newt' is the DNS name of my windows box to which I'm telnetting.
hope that helps
YMMV
ps. a better option would be to install an ssh server on windows.