CVS on single NT machine -- username mismatch?

[R]

        I have used cvs on a Unix machine for a while, now I would like to 
use it on a Windows NT machine -- but not as a server/client setup, just 
for a single user on a single machine, and I am quite happy with using a 
command-line version rather than installing several other packages to allow 
gui use. However, when I install the cvs.exe downloaded from cvshome.org, I 
get the message 'your apparent username is unknown to the system' 

I don't understand this, because I am logged on to the system with a local 
user account, and the username echoed by the message is correct; where is 
it mangling it .. and .. how can I work around it or fix it? Preferably 
without installing more software packages.