need to roll back Ubunto 12 -> 10

Have you considered Xubuntu or Lubuntu? They both require less resources than Ubuntu. To go back to Ubuntu 9 or 10 will not work, they are no longer supported. I have a Dell 1.4 processor and 1 Gb ram, it runs Xubuntu 12.04 very well. Does not run Peppermint good (based on Ubuntu 14.04). If your ram has been upgraded to 1 GB, I think Xubuntu or Lubuntu will work.

There is no Ubuntu 9 or 10 or 12. There is:

Ubuntu 9.04 (EOL on the desktop)
Ubuntu 9.10 (EOL on the desktop)
Ubuntu 10.04 (EOL on the desktop)
Ubuntu 10.10 (EOL on the desktop)
Ubuntu 12.04 (LTS and supported til April 2017)
Ubuntu 12.10 (EOL on the desktop)

As you can see "Ubuntu 12" doesn't exist.

I suggest you wipe the install you have now and do a clean install of Trusty. Trusty (Ubuntu 14.04) is LTS and supported til April 2019. You can restore your user data from backup.

thanks all. the revision# is not the point, and this laptop can't run 14. its CPU / mpu is missing features expected in14.
I may re install 9 from cd and update to 10. 12 has high speed network drivers but I don't care for its desktop, it was a
mistake to upgrade and I wish it was blocked just as 14 on

David
If you reinstall and try to update, all repositories are removed. There will be nothing to update from. Also, the last two numbers are very important. You can run Ubuntu 12.04, but 12.10 is not supported in any way. I also do not care for 12.04's desktop, you can change to other desktops, I use Classic. Please read site below.

http://askubuntu.com/questions/65083/what-kinds-of-desktop-environments-and-shells-are-available

What are the missing features, your computer does not have to run 14.04? If you were using 14.10, it is not ready to be used. Again Ubuntu 12.04 and 14.04 will need 1GB of ram. More if you have integrated video.

The digits after the dot in an Ubuntu release number are no revision number, but an integral part of the version number.
As there are two completely different versions of Ubuntu published every year, there is the need to indicate which of these releases you are talking about. The digits in front of the dot indicate the year, and those after the dot the month of publication.

Ubuntu 12.04 (published in April 2012) is still supported, but Ubuntu 12.10 (published in October 2012) is not!

Remark, for long-term-supported releases of Ubuntu there are sub-version numbers to indicate the revision number, e.g. 12.04.5 or 14.04.1. Those can mostly be neglected when talking about general requirements for running such release.

I'd suggest you do a clean install of Xubuntu 14.04. If your system can run 12.04 then it will run 14.04

Upgrading between releases can generate issues and a clean install is much less problematic. You will probably find your system will run the default Unity session in a clean install of 14.04

firstly - Thanks for all the responses and observations. let me save on the mental anguish... the issue seems to has been the
advanced Ubuntu dispaly (Unity-3 or such!); I've loaded a driver detected by the system scan while in low res / recovery mode
since the screen was scrambled like old TV ... with that driver (some NVIDIA 179 ..?) the screen looked quiet
sharp; but Upbuntu didn't restart, didn't shut off.. had to hold down the pwr button ...anyway - it's Ubuntu 2D that I should
choose off the welcome login screen (as this one always came up nice and clean).
--
so, 12.04 LTS it is; and works just as I recall 10.nn and better. I hope my Q and notes helped others :)
Thanks.