How to restore default Ubuntu desktop

[Tommy Trussell]

How do I restore the default Ubuntu desktop panel arrangement or
revert to a previous one after I make a big mistake?

BACKGROUND:

I successfully upgraded a system from Warty to Hoary with no problems.
(I followed the steps at
http://www.ubuntulinux.org/wiki/HoaryUpgradeNotes and elsewhere.) I
puzzled out how to get my screen depth and resolution reset to the way
I like it (if there's a GUI way to change the depth, I didn't find
it).

HOWEVER, I was going back again to try to follow the step 4: "Start
update-notifier and save your gnome-session..." and I couldn't find
the update-notifier.

So I started the Ubuntu Updates tool (the simplified frontend --
whatever it's called) and discovered it doesn't allow you to start it
with gnome-session.

So for some strange reason I right-clicked on the top panel and
deleted it. I made sure I didn't have the "save session" checked and I
figured the panel would return when I log out and back in. WRONG!

WHAT I TRIED:

I tried dpkg-reconfigure ubuntu-desktop, 

I've dug around in the ~/.gnome and ~/gnome2 directories, but I don't
know where to look.

I tried googling, and didn't find this problem (my apologies if it's
in a FAQ somewhere).

I decided the next step might be to create a new user and copy some of
the settings files from that account... but I decided to ask here
first.