OK, the easy way to determine what kind of file a file is, type:
at the prompt, such as "file hosts" without the quotes, and it should return the format. Usually in /etc this will be "ascii text".
you can edit this (as root - type "su" and then root password) with a command such as "gedit hosts" in GNOME, or you can use Kate in KDE.
You can also use vi, but that isn't the most user-friendly editor.
Follow these instructions to use vi:
Password: (enter root password here)
# file hosts
# cp hosts hosts.BACKUP
# vi hosts
This will open up a command line editor called vi - follow these key presses carefully:
Press ESC once.
Press I - Something like --Insert-- should appear the the bottom of the screen.
Use the cursors to move towards the current hostname. Use backspace to remove, and type your new hostname.
Press ESC twice.
type: ":x" without quotes and press enter. That will now save the file.
That is how to edit - I am not sure if this is where you need to edit the hostname, but have faith in nx5000 and let us know if you succeed!