It sounds like something went wrong with your installation. Can you do anything
or is it hung? Try right clicking on the desktop. If you get a drop down then
try scripts > Terminal here. Then you can do this then use apt-get to reinstall
or launch Synaptic with sudo apt-get install ubuntu-desktop or sudo synaptic and
do it from there.

You can also try Alt+F2 and type Synaptic in the window that opens. This may not
work depending on how messed up Gnome is.

Failing this, I would go back to the Live CD (8.04) and then back up all of your
data from /home/username to a usb key/ DVD or other drive. Then you will have to
reinstall 8.04 and perhaps stick with that until you get a handle on what
happened.

If you had the 8.10 CD then you could try to install it, but without that you
must first install 8.04. I would consider downloading the 8.10 CD if you are
serious about trying it. Upgrades are always with risk, even from Windows to a
newer version. That is why they recommend that you backup before you change your
system. Same could be said for Linux.