So you want to wipe your hard drive clean and reinstall a fresh Ubuntu copy. Before you do that, it might be wise to make a list of currently installed packages and reinstall them in a jiffy afterwards on the new OS:
sudo dpkg --get-selections > package_list.txt
Save the text file on a thumb drive, format the drive, reinstall Ubuntu, then to a
sudo dpkg --set-selections < package_list.txt
sudo apt-get -y update
sudo apt-get dselect-upgrade