dns mess after altering hosts file

i was trying to add a host name (just to try it out) on the "hosts"
file, first i tried to set it on the c:\windows\hosts file and then on
the c:\windows\i386\hosts file. from that moment on (and after several
changes on them and several restartings of my computer) thigs went out
of control... localhost is not being resolved if i don't type
"http://" and, when i do it, local adresses are resolved in a remote
DNS!!!!
there's still more!!! i can't connect to my ADSL ISP anylonger from
the XP User i made those changes... i actually had to switch to
another user, connect to my ISP and then switch back to my user. this
really exceeds me...
any idea of who to make this go back?

my advice is NEVER EVER TOUCH HOSTS FILE IF U DON'T KNOW HOW TO DO
WITH IT!!