Mount of filesystem failed

Look in "/etc/mtab" if there is this external hard disk.
Which is the name of failed file system ?
It should a name like sda1 ou sdg1.

I'm using now vista as as i cant start ubuntu

At the first booting option i get this message:

       [ 0.904664] kernel panic - not syncing: VFS: unable to mount root fs on unknown-block(8.2)

At the second + third booting option i get this message:

       Mount of filesystem failed.
       A maintenance shell will now be started
       Control+D will terminate this shell re-try
       root@ubuntu:~#

and when i enter "/etc/mtab" the answer is than: permission denied

I didn't find sda1 or sdg1 or anything else.

I cant start ubuntu would make sense to uninstall ubuntu
uninstalling ubuntu would i do this just by deleting the ubuntu file in my computer - vista;
and could i than again install ubuntu from CD ???

Firstly, do you have data to recover ?

How did you install Ubuntu ? (I heard of an installation inside Windows disk I never tried)
If it is a true installation, how is partioned disk ?
This is important to get back data or to reinstall Ubuntu ?

i installed ubuntu about 3 weeks ago and i keep all my data on external harddrives. so there is not a lot to loose.
I installed ubuntu from a cd which i got from a friend and it did run well until now. i believe i played once around with the mounting
option and that's where it started.
my laptop came with vista so and i put the cd in and i had the option to install on my laptop or work it with the cd.
I tried this too but ubuntu is very slow(not recommendable).
It's good to have both vista & ubuntu.

If Vista is OK and all data are on an external drive, the easiest solution is to reinstall from scratch Ubuntu.
However, as status of Linux partition is not sure, I recommend to format the Linux partition.
If you want to get back user software configuration, you will find at home directory a lot of files which begin by a dot.
To see them, do "ls -a", or modify case "View hidden file" in file explorer.
You can save them before Ubuntu installation, and copy back after.
Reinstallation will do again the mounting table and grub configuration.

If later you have data on your computer, do a backup of home directory.
Some person do a separate partition for "/home".

If it is OK, please close the question.

Else post a new message with new data about issue.

Thanks for your help.
After reading your reply i've used my cd again and started downloading.
Just before finishing i cancelled the instalation and shuted my laptop down and restarted than i had my usual option to start ubuntu.
I have three option:
        - using the first option i get this messages on the booting sreen:

         [ 0.904664] kernel panic - not syncing: VFS: unable to mount
         root fs on unkown-block(8.2)
         do you've a idea how to solve this problem?

        - using the second option: ubuntu started without a problem and my
          data is still there

        - didnt try the third option yet

Thanks for your help.
After reading your reply i've used my cd again and started downloading.
Just before finishing i cancelled the instalation and shuted my laptop down and restarted than i had my usual option to start ubuntu.
I have three option:
        - using the first option i get this messages on the booting sreen:

         [ 0.904664] kernel panic - not syncing: VFS: unable to mount
         root fs on unkown-block(8.2)
         do you've a idea how to solve this problem?

        - using the second option: ubuntu started without a problem and my
          data is still there

        - didnt try the third option yet

If you use a grub less then 2.0, In file /boot/grub/menu.lst can you post the two blocs corresponding at two first options ?
Else can you post what is display in boot screen (kernel version, mode normal or recovery) ?
Can you check the boot file in first menu exists ?

Hi delance,
sorry i was quiet busy.

when i select ubuntu as op system i come into the boot screen similar to this:

                                         GNU Grub version 1.97"beta4

Ubuntu, Linux 2.6.31 - 17 - generic
Ubuntu, Linux 2.6.31 - 17 - generic (recovery mode)
Ubuntu, Linux 2.6.31 - 16 - generic
Ubuntu, Linux 2.6.31 - 16 - generic (recovery mode)
Ubuntu, Linux 2.6.31 - 14 - generic
Ubuntu, Linux 2.6.31 - 14 - generic (recovery mode)
Windows Vista (loader) (on/dev/sda2)

when i start the first option: Ubuntu, Linux 2.6.31 - 17 - generic

then i get this message: [ 0.904664] kernel panic - not syncing: VFS: unable to mount root fs on unkown-block(8.2)

This happened after i started(a while a go) mount but then i interrupted the process.

and by the way i lost the data from the last file i worked on a EXCEL the file is still there.

Use "Ubuntu, Linux 2.6.31 - 17 - generic (recovery mode)" which is second option.
Do a "fsck /dev/sda3" with changing sda3 by name of partition with Ubuntu. BE CAREFULL: it can be very long.
Fsck should display a %age of progession.
If fsck tell there is a problem, but it can't restore partition, save the data you can, and format the partition (the root table is damaged, and you need to erase all).
To know the right partition, you can use Gparted, and see which partition is ext3 or ext4.

N.B.: your question is marked "solved".

yeah i marked it solved as i can use this option:

       Ubuntu, Linux 2.6.31 - 16 - generic
       Ubuntu, Linux 2.6.31 - 16 - generic (recovery mode)
       Ubuntu, Linux 2.6.31 - 14 - generic
       Ubuntu, Linux 2.6.31 - 14 - generic (recovery mode)
       Windows Vista (loader) (on/dev/sda2)

sorry if that wasn't correct to marke it as solved i'm quiet new to ubuntu and i was quiet happy as i could use ubuntu in the above options again.

I might let "Ubuntu, Linux 2.6.31 - 17 - generic (recovery mode)" run tomorrow night. I hope that will be enough time.