new vid card - machine halts

[Ken N9VV]

Hi, I installed a 64MB Nvidia GeForce4 MX4000 PCI card in my PC. It 
works perfectly (really beautiful) in Windows.

But when I TRY to boot into Ubuntu, the "unpacking of the OS" step is 
where the system freezes. I have no keyboard or mouse input. Only a hard 
reboot (power cycle) brings me back to the Grub menu.  The system was 
working perfectly with the mobo Intel chip display for both Windows and 
Ubuntu. I (mistakenly) thought I could change PCI cards and run Ubuntu 
in some crippled VGA mode whilst I set the right X parameters. But, no joy.

(1) how do I boot to single user and
(2) try to convince Ubuntu
(3) and X that I have a new vid card?

any ideas welcome,
thanks,
Ken