Nvidia graphics card problem?

[Graham Todd]

I have an amd64 based machine with 240gig hard drive space on two
drives (using 32bit machines, I used one drive for my /home directory
and the other for all else), 4 gig of ram, and a nvidia graphics card.

When I run the 64bit live CD, everything runs as it should and I get
the desktop and notes plasmoid up OK.  However, when I install it, on
rebooting I get the log-in screen, log in then get a completely white
screen then a black screen with a dark grey rectangle at its centre,
then the rectangle turns white with the top corners rounded.  After
that it freezes.

I've raised this subject before and got some replies but I stupidly
erased everything in my folder before I'd archived it....  I remember
somebody suggesting the fault would most likely be the graphics card.
Does that mean I'll have to install the nvidia drivers?  And how should
I do that when I can't get into KDE?

Or is the fault with the legacy settings in th~/.kde folder?

I'm currently use Ubuntu 8.10, and all is well but I don't like the
Gnome interface.  Can someone help me to get back to KDE?

TIA.

-- 
Graham Todd