host file problem

using xp2

have windows\system32\drivers\etc\hosts file with ip addresses for
network systems. Using 192.168.20.xxx

192.168.20.200 franks.sss.org franks
192.168.20.201 bills.sss.org bills

ipconfig give following info.
however my system "franks" is 12.64.xxx.xxx when logged into isp
and 127.0.0.1 when not.

This worked fine on NT4. What am I doing wrong.