FTPD and Internet Explorer 6.0

[Super Daemon]

I've been curious about this for a while. I have a freebsd 5.3 Release
Server running FTPD. Users running MS WIndows can connect to it just
find as long as they type in ftp://user@ipaddress. However, when they
connect as ftp://ipaddress, the server thinks they are trying to
connect anonymously. But i've noticed that  this doesn't happen when
running PROFTPD from the ports. Can anyone explain why this is??? Is
there a way to connect as ftp://ipaddress and still get prompted for
username and password under internet explorer 6.0???

I'm not on the list so please CC: me. 

Thanks in advance!!