You might want to read up a bit on de-installing programs from the commandline.
When issuing a command that requires root privileges (and installing or
deinstalling does) you need to use sudo in Ubuntu. If the command prompt is $
then use sudo first in Ubuntu.

Here is a deb guide:
www.debian.org/.../ch-dpkg.html
or
linuxhelp.blogspot.com/.../...-primer-for-new.html
More detailed dpkg explanation: http://linuxreviews.org/man/dpkg/

You can use sudo before the command or you can temporarily change to root with
sudo -i. You will see the prompt change from $ to # as you go from user to root
level.

If you are asking yourself why you are using the commandline, this is punishment
inflicted on unwary users who get into problems by wandering off the beaten path
by downloading bad deb files and installing them instead of sticking with those
in the repositories. Not really. :) It is a powerful tool where you can use
switches and wildcards that aren't available from the GUI. Sometimes apt or dpkg
will break if you install outside of the repositories and in those cases you
need a powerful tool to get out of it. I have done this many times, so take
heart. It can happen to anyone. You can protect yourself in the future by
sticking with known entities. Sorry for needling you about this. However, once
you are able to fix problems then you can allow yourself more freedom to get
into them in the future.