Thanks for your time Klaus.

I have tried with cheat code 'knoppix no3d', the machine now stops during boot with error

'grep: /etc/x11/xorg.conf: Input/output error

I think, to avoid wasting your time, I will start from a fresh install and follow your instructions again to install the nVidia driver and see what happens.

I should mention that I use the ADRIANE-KNOPPIX_V7.2.0g-CD-2013-07-28=EN ISO in case this has any bearing on the matter.