change of user in ssh session of windows

Hi,

I installed COPSSH 1.4.1 in my windows machine to make it working 
as server. I created & activated the users as per the instructions
given.
Everything works fine.

Now my requirement is that, in the opened (established) ssh session 
of windows, I want to re-login as some other user.

See the scenario below:
-----Clip-----
C:\>ssh [email protected]
[email protected]'s password:
Last login: Fri Nov 24 13:52:09 2006 from localhost

root@4FID01455 ~
$ su - vamsikp
-bash: /bin/su: No such file or directory

root@4FID01455 ~
-----Clip-----

For this, what we usually do for linux is "su - <user>" which takes 
to the specified user shell after successful authentication.

But in COPSSH, I didn't find "su" utility.
I installed GNU UnxUtils in my windows as well for having the unix 
kind of utilities & I find "su" as well there. But it doesn't have any 
association to the local/domain users in the machine. It complains 
that the user does not exist.

Can anyone suggest as how to do this?

BR,
- Vamsi.