to telnet to a dm600 this is what i do.
firstly if you are going to use this method you need your dreambox connected via a router to get the ip address after deleting the bootloader and dhcp enabled via the comunication setup menu on the dreambox.
in windows xp...
clic start then run.
in the run box type cmd and then clic ok
you should now have a dos window open.
type in there type
telnet 192.168.2.2
replacing the ip address i used as an example with the ip address of your dreambox then press enter.
you now need to login to the dreambox
type root as the login then press enter
dreambox as the password then press enter
you should now say root@dm600pvr ~ #
you are now ready to delete the bootloader by using this telnet command
mount /boot -o remount,rw
rm /boot/*
reboot
now the dreambox will reboot and is ready to be flashed via a web browser.
open internet explorer or firefox
and type in the address bar the ip address of the dreambox
again press enter and you should see a page where you can now flash your new image to the dreambox.
(if you dont know the ip of the dreambox it can be found via your router setup menu, on the dhcp client list page.)
hope all this makes sense?
if not stick to other methods of flashing