Hi, put it in /root/.ssh/authorized_keys. I don't know if it works with the key produced by Putty, but with a "ssh-keygen"-generated public key it does. If you need more public keys to log in, simply name the key files /root/.ssh/authorized_keys2, /root/.ssh/authorized_keys3 ...
Regards, Hauke -- Stoppt TCPA, das Zensursystem von Microsoft! http://www.againsttcpa.com