Dear All,
I have a laptop with Ubuntu 9.10 installed. It will not boot to the login screen. If I remove this HDD and connect it as a secondary drive to another PC running Ubuntu, will I be able to access the files on this HDD? There is a lot of data which I haven't backed up which I need to retreive. I don't think the hard drive has failed.

Thanks in Advance,

Dave.

yes you will. you will just have to mount it somewhere.

One problem might occur : The filesystems are all different like xfs, ufs, jfs, ext2, ext3, ext4, reiserfs etc etc.
A Linux OS on a PC that is installed on ext3 two years ago might not be able to mount a new ext4 partition. It also will have difficulty to read and write there. Als grub must have support for the filesystem to boot; e2-binaries are to be found at /boot for example.
A crunchbang 8 on ext3 or ext2 I tested was not able to look into a Puppy on ext4. And at grub boot-prompt >root (hd0,3) >find /boot/pressTAB just showed something like <_|_________________________________________________________________________________________________ ____________________________________________________________________________________________________ ____________________>
empty shadow/hidden/ like. I could move the cursor at this line but no character was visible.

You could also use a recent live distro on the original computer without removing the drive. It should be able to handle any filesystem you have. You may also be able to repair your installation so that you can boot again.

Just drop a modern Linux Live CD, mount the partition, hook up an external disk and copy whatever you want to salvage.

Better still use the Live CD to repair the boot loader and make Ubuntu bootable again.

Assuming something is wrong with the laptop and nothing (including contents) is wrong with the HDD, the OP's original question is on target. A liveCD also wouldn't boot.

If a liveCD would boot, using that as jschiwal and saikee suggest is probably easier and safer than taking the HDD out to plug into a different computer.

Once booted in a liveCD, copying files across the LAN to another computer might be the most robust way to get the data off.

But assuming the laptop is basically OK and the failure to boot the HDD is because some GRUB or Linux files are corrupted, fixing those files from the liveCD is the best solution.

If it is failsafe:
login:
passwd:
startx
twm
kdm
gdm
xwm
xorg
xorgsetup
xf86config
xfree86-cfg
apropos
cd / / / change directory
ls
could fix x-server problems like freezing. / mounted read-only might also lead to crash because some programs and servers want to write even temp o rary files on the HD.
The Ubuntu X-config binary I donot remember at the moment. I am testing absolute, slax, zenwalk at the moment.