New user problem

I installed Ubuntu9.04 fresh, then installed eucalyptus. Now, when I boot Ubuntu and open terminal it says rajeev@localhost, that is it doesn't log me in as admin (I've set it to automatic login)
my system name is 'nix'. previously, when i use to open the terminal it said rajeev@nix

Also, now all startup programs don't open, like Network manager doesn't open and I'm not able to logon to the internet. That is I'm not admin, it doesn't allow me to open user and groups tab under Administration.

I haven't used or worked in server environment before, I would like to go back to Ubuntu single desktop again. Do you know a way of fixing this?

My system info is:

Release: 5.0
GNOME: 2.26.1 (Ubuntu (2009-05-06)
Kernel: 2.6.28-13 generic (#45 - Ubuntu SMP Tue Jun 30, 19:49:51 UTC 2009)
OS Type: Linux
GCC Version - 4.3.3 (i486-linux-gnu)
Xorg - Unknown
Hostname - localhost.localdomain

Now, I have uninstalled eucalyptus from package manager. Please let me how to connect to internet and work as an admin.

Thanks a lot.