don't use telnet, its rubbish and a huge security risk. use openssh which uses encryption to make it safe but still works the same way as telnet.
go here http://www.openssh.org/portable.html
to get the linux version (you need the server running on your machine to access it from somewhere else [the same as telnet]).
then go to their main page and click on alternatives for windows which should take you to a place to get a windows client to use (telneat looks good).
there should be info on the site to tell you how to install and use etc.
hope that helped