FTP site config.

I am set up an ftp site on my windows 2000 server, but when I test it ftp localhost it gives me an error message unknown error number. Or when I change the ip addres it gives me the error of the coneccion being terminated from the server. I follow the steps mentioned in techrepublic but is not working for me. For the IP address to use, Should I use my WAN ip?
is there any other settings that I need to be aware of. Thanks in advance for your help..