I have a 80 GB hard-disk also After some trials in which I messed up my
computer I made the installation in the following way: I booted from the Windows
CD, wiped out the partitions, then made a 20 GB C partition, a 40 GB D partition
and I left the rest unpartitioned. Then I installed Ubuntu on the unpartitioned
hard-disk by choosing the option "Use largest available free space" This is the
best method, I think. Do not touch the red cursor on top because you might mess
up your Windows ( I did twice this mistake).
If you have 3 Windows partitions just copy your files from the third partition
somewhere else, delete the third partition by using a Windows CD, quit Windows
setup, reboot, boot from the Ubuntu CD and then install Ubuntu on the "largest
available free space".

I forgot to say, I now Windows is installed on partition C, I have most of my
files in partition D and I have Ubuntu on the rest of 20 GB hard disk space.
When I start the computer, GRUB loads, then there appears a menu from which to
choode the operating systems to start. Ubuntu is the first and Windows XP is the
last.
Both have great advantages. Ubuntu is great for writing files to CD or DVD and
for printing. You can also manipulate or delete any of your files in the Windows
partitions from under Ubuntu. You can recover your files from anywhere in case
Windows breaks down.
I need Windows only for the Internet (our ISP does not have the technology for
using Linux) and for writing in Word and Excel. Open Office is not at all
widespread here.

Your operating system has nothing to do with connecting to your ISP. I
am not sure where you got that from. And Open Office has the option
to save file in M$ Office format. So, it doesn't matter how
widespread OO use is really.

Thank you. I did not know this about Open Office. Very nice.

Yes!!

But be sure that you are installing ubuntu in correct partition. By the way
whats the version of ubunu that you have. I recommend a newer version ubuntu
7.10.