Upgrade Ubuntu 11.04 to 12.10 (nvidia problems)

After having successfully upgraded my desktop, I did the upgrade from Ubuntu 11.04 (Natty Narwhal) to 12.10 (Quantal Quetzal) on my laptop. Unfortunately this cannot be done in one step, three complete upgrades have  to be done:

1. 11.04 to 11.10
   no problems occurred. 
2. 11.10 to 12.04
   The x-server could not start up. The screen just changed from green to red, from red to orange and so on ...
   Somehow the nvidia driver modules were removed. To recover from this I had to reboot in "recovery mode" and to select "basic video".
   Once this was done I installed the nvidia driver again and the module was added automatically to the kernel. Now rebooting worked nicely and the nvidia drivers are running again.
3. 12.04 to 12.10
   ongoing ...