If you can boot from a USB key then you can create a start up disk from
Start-up Disk Creator (comes pre-installed in Ubuntu) or Unetbootin (you'll
need to install it from the repos). You will need a downloaded ISO for the
first option, but Unetbootin can download one and install from that.

If you can't boot a usb then you will need to burn the ISO to a CD or DVD.
The Ubuntu website help.ubuntu.com gives you help on both of these options,
plus lots else.

To start fresh you will want to format your partitions. Backup data before
you do anything unless you do not care about losing data.

Suggestion: Go with two partitions for Ubuntu, one for /home and one for /
(root). You will need to a manual or custom installation (last in the list
of choices). You need to know two things. Partitions need a file format
(choose ext4) and mount point (choose /home for home and / for root). Root
does not need to be large, 10 or 12 GBS is plenty for most people. Home
should be larger.

You only need to format /home once and you will preserve your data and
settings for as long as you like. It makes subsequent installations a
breeze. (In the future you choose manual installation again, and do
everything the same, except you do not format /home).

Clean installation can be done from the live CD
without formatting ! The easiest way: Boot up the live CD, then give the command
sudo nautilus in the Terminal and access the hard disk. From there, delete all
the folders except for the Home folder. Enter the Home folder, click on View,
Show hidden files and delete everything that begins with a dot ., like .emerald
, .evolution and all the other system files that begin with a dot.
 Then, install Ubuntu with the last option of the installer, manual
partitioning or something like that. There do not check the option for
formatting your partition and such you will do a clean install with preserving
all your data.

Formatting is so much easier since you are going to be using the Live CD's
partitioner anyway. It is one mouse click to check the format box. Using
Nautilus works, but it is way more work. Besides, Maverick has a new
installer and there is no need to boot all the way to the desktop.

When you delete all the hidden files don't you lose all the packages
that you had previously installed?

Related but separate question - How do I preserve all the packages that
I have previously installed? Do I have to manually reinstall each of them?

There are two answers to the problem. It depends on if you have a broadband
connection which is easier.

I save the list of all of my installed applications to a text file using
Synaptic, save Markers in the menu. Then I re-install but keep my home
partition as is (one reason to have a separate home partition), otherwise
you need to save the file to a usb key. After installation, I fire up
Synaptic and choose Read Markers and navigate to the text file. It then
proceeds to download and re-install all of my applications. It takes time
and as I said you need a broadband connection with no limits which i have.

The second way is to back your apps up to DVD using AptonCD which is in
the repositories. This method will only work if you are re-installing the
same version. If you are moving to a newer version then use method one. If
you try to install old version apps onto a newer base, then you are likely
to run into dependency errors and destabilise or even break your system. Not
fun!

Generally, the hidden files contain settings and data specific to the
application, but not the programs themselves. I think deleting the hidden files
is a bad idea, if you plan to re-install the applications.

To make a list of all your installed packages use this command:
dpkg --get-selections "*" > Desktop/applications
(it creates a text file called "applications" on your desktop.)

To install all the packages, use these commands:
sudo apt-get update
sudo dpkg --set-selections < Desktop/applications
sudo apt-get -u dselect-upgrade

Before doing the re-install, I usually go through the text file and delete most
lines, because it will contain each package in a default install, libxxx files
which are to resolve dependencies, and stuff I installed and then lost interest
in. It's not a trivial task, because the file will probably contain over 1500
lines.

That's the info that I was looking for. Since I didn't have this
information earlier, I did an upgrade rather than a clean install. The
upgrade went well.

Download the ISO for Ubuntu 10.10 if you haven't got this already and
create the installation CD then boot the system with this and install
from there, using the option to 'take over the whole drive' to erase
everything that's currently on there and just have Ubuntu.

Welcome to 'Al Fresco' computing .... no Windows

If you've already upgraded to 10.10
cant you simply use System Administration / Gparted
and then reformat the windows partition,
and then use it as a data partition?

or delete the windows partition and then resize the ubuntu partition from a
live cd?

Are you planning on just reinstalling or are you interested in eliminating the
dual boot windows partition. The second option should be interesting and I hope
to hear the gory details of how you do it.