Woops did it again.

[#1]

Managed to delete gnome 3 session by mistake with synaptic while trying to sort out some desktop issues. Now I can't login to a desktop  is there a way of re-installing it using a liveCD? Really tempted to do clean install right now but not sure if my Home which is on a different partition will keep all my software settings.

[#2]

Does your system boot to LightDM (or other Dispaly Manager) or to a command prompt?
If it's the former press CTRL & ALT & F2 together to switch to vt2 and log-in there (if it's the latter, just log-in ).

$ apt-cache search gnome-session
gnome-session - GNOME Session Manager - GNOME 3 session
gnome-session-bin - GNOME Session Manager - Minimal runtime
gnome-session-common - GNOME Session Manager - common files
gnome-session-fallback - GNOME Session Manager - GNOME fallback session
gnome-session-canberra - GNOME session log in and log out sound events
$ sudo apt-get -u install gnome-session

[#3]

Keeps saying login incorrect!

[#4]

Really strange one.  Pressing CTRL & ALT & F2 asks me to login but when I enter my user name and password it says they're incorrect. Removing  fallback was ok, went pear shape after removing gnome3. I was hoping I could checkmod in using a live cd but I still have the driver issue with nvidia divers. Is there anyway that I can install the drivers to the live cd using another ubuntu system or anyone know why it's saying myuser name or password is wrong?

[#5]

If you can't log in then you need to try a chroot from the live cd, then re-install the gnome stuff.

[#6]

  Chroot, that's what I meant. Was a bit late! Problem I have is using the livecd, I created a live usb stick using my new netbook using 12.04.2 which supposedly solves the nvidia driver issues but I get to the login screen and it goes off with drm nouveu gpu problems. I updated the live stick and tried to install the drivers to that using another computer(stick has persistant file) but it said dependancies not met. I guess because it has a different g card. Ikve seen it suggested to enable the built in graphics boot up and download the drivers and it should be ok on the next boot but I'm not sure if the pci g card is not running whether it will let me get the drivers on the stick or which driver version to get. There are three! Other than that my other option would be  creating a lightweight boot up stick like lubuntu, getting stuff off that isn't in the cloud and going for a fresh install using alternate cd which got round the driver problem in the first place. Would still like a working 12.04 live cd though if I can for moments just like this. So glad I kept my home seperate now so cheers for that HB.
I could take a chance and just go for a fresh install but if I lost the home drive I'd be gutted. Do you know if ubuntu is the only distro with this nvidia card issues or it affects others?

[#7]

I personally don't have any issues with my NV card, a GT 610, with Mint 14 or 15. IT does start with nouveu, but on 15 run the MintDriver and install the latest NV driver from there.
As long as your /home is on a separate partition then when you install choose "other" and set it up as /home and ext4 (or why) and NO FORMAT, and it will keep it intact.

[#8]

Home is on a different hdd altogether. Bit nervous about doing a fresh install using the alternative disc its not as intuitive as the live cd. Ill see if I can get a couple of things off first to be on the safe side. Fresh install best option I reckon. Since trying a few DE's I get the screen going of after start up so just after a fresh start.

[#9]

You don't need the alternative disk, just choose custom install instead of default.

[#10]

The live cd doesn't work on mine mate. I think you once told me to use alternate instead and that worked.

[#11]

Yuck no live cd.
Do you have a floppy on it? You can make a floppy based boot disk for the cd. You will have to google for it as it has been many many years since I used floppies.

[#12]

Just trying lubuntu livecd at the moment to get stuff off before formatting IF it works. Just wondering if I can chroot with it to put gnome 3 back on and what would the code be to reinstall. If I can get back to gnome I can make sure I have everything and re-install at leisure.

[#13]

You guys are going to have to excuse me being a K*OB  Waldo nailed it post 2. Seems that my user name is not the same as the name I login to on the GUI at start up. Major Face Palming going on here with the biggest of palms and the smallest of faces. 
I swear I will get to the bottom of this LiveCD Caper though. I'm sure someone in here said about downloading the drivers and copying them over to the USB stick somehow. In the meantime I'm back. The monitor going of at the first click of something on the desktop is still happening which is the reason I was deleting DE's and got myself in this position in the first place. Maybe I should also look at graphics drivers, I have attached a list of available ones.
On another note, I came across some info on how to totally uninstall everything that was installed at the time by going back into the history logs. I had that many that I couldn't find when I installed the de's so I guess there may be leftover stuff. Maybe will do the format anyway but without the pressure of having to get a working system first.