How to shrink root file system (LVM) in Linux Fedora 9?

My root file system is of type LVM. i wanna shrink it but unable to do so.
When i give the below command:

resize2fs /dev/mapper/VolGroup00-VolLog00 10000M

it messages that online shrink can't can't be done as the logical volume is mounted on /. i switched to single user mode by giving command:

shutdown -i 1 now

There also, it messages the same. it says that online resizing(shrinking) is not available.

i tried by giving a few commands below but my system messaged that command doesn't exist. ( not sure whether these commands are really there or not, just a try)

ext2online /dev/mapper/VolGroup00-VolLog00 10000M
ext2resize /dev/mapper/VolGroup00-VolLog00 10000M
 /

What i intend to do is: i w'd reduce the LVM and the space avalialble after that , i w'd make one more logical volume in which i w'd install Ubuntu 12.10. i hope i can install this way keeping Fedora as well as windows.

Shrink requires an unmount of the filesystem and since it is the root filesystem it cannot be done in the way it is done for none root filesystems.

Go to rescue mode using a bootable media ( First CD) and.
Do NOT mount /mnt/sysimage, press skip on this step.

You would be directed to rescue shell, In rescue shell do the following

a] vgchange -a y VGNAME
b] e2fsck -f /dev/VolGroup00/LogVol00
c] resize2fs -f /dev/VolGroup00/LogVol00 Size(in M,G)
d] lvresize -L Size /dev/VolGroup00/LogVol00 

Thanks, I am going to try how it works and w'd update you. In the mean time, just w'd like to know whether my all 3 OS w'd work. Now, 2 are already there, windows and fedora.
When I boot it asks me for the below options:
Fedora
Other
(by default it selects Fedora)
If I select "other", it takes me to windows.
Now, what I am trying to do: I w'd go via unetbooting and then I w'd install my ubuntu 12.10. Now, when I free up some space in root directory, I w'd select that space for installation. So, can you please let me know whether all the 3 OS w'd work and will ubuntu be my boot OS.

---------- Post updated at 08:41 PM ---------- Previous update was at 07:46 PM ----------

OH MAVERICK IT HASN'T WORKED!
I WENT THE SAME WAY YOU TOLD, SKIPPED AND DIDN'T MOUNT THAT. THEN I ENTERED RESCUE MODE. HERE THE COMMANDS DOESN'T WORK.
When I entered the command

vgchange -a y VolGroup00

, it messaged that the command doesn't exist.Not only this, other commands like vgremove, pvcreate, lvs , pvs, mkfs also failed to run with the same message of invalid command.