First, I'm not a Linux person, so much of this is new. Expecially using FDISK.
So bear with me. I'll try to explain what I'm trying to do and where I'm stuck.

My problem really doesn't have any problem to do with CentOS 4.8. It's really a
case of being totally confused by installing Ubuntu for dual booting and the use
of fdisk or the install programs to create partitions.

I have CentOS installed, with a non-graphical interface. I want to install
Ubuntu as a dual-boot option. But I'll be darn if I can figure out how to do it.
I've installed each one seperately using the entire drive but need it to be
partitioned for both.

When I try to install Ubuntu, my first problem comes from Ubuntu not being able
to detect the CentOS OS. It says there is no OS but I know there is.

Problem 2 is that I can't figure out how to do the partitions to allow Ubuntu to
be installed in a different partition. This is a lack of understanding of fdisk
and the specific options to get what I need. There is a lot of terminology that
I don't understand.

From what I understand, I will need at least 3 partitions. One for CentOS, one
for Ubuntu and one for a SWAP file. But how to make them, with fdisk and the
types. Seems to be a lot of partition types. At least that's what I see when I
use the install program to look at the partition table.

I have not been able to figure out how to do this partitioning, after one of the
OS is installed. So, it appears that I will have to partition the drive, before
installing either one. But how to do it and what types of drives, mount points,
etc.

What I need is:

1) A 10G partition for CentOS
2) A 4G partition as a SWAP drive
3) A 146G partition for Ubuntu
4) And all the other logical stuff that goes along with the above.

It's confusing to me, what types of partitions I need, mount points, commands,
etc. I've been trying to do some reading on this but everything seems to start
with the assumption that the reader understands Linux. Bad assumption.

When I install CentOS, it creates a partition table something like:

VG VolGroup00 165928 VolGroup
LV LogVol01 1984 swap
LV LogVol00 154944 ext3 /
/dev/hda
hda1 101 ext /boot
hda2 156963 physical

I have tried every which way to use the partition creater in the install to
break the 160G drive into two other partitions, without success. I only need
about 10G for the stripped down version of CentOS. The rest should be available
for use by Ubuntu.

Perhaps the best thing would be to create the partitions and then perform the
installs. But how is a mystery?

Does someone have the time and experience to give me some specific detailed
instructions on how to setup the partitions, on this 160G drive, to allow these
two install programs to run and for me to be able to select which partition to
install them on?