For those who may need the pointer,
I've sorted out my nvidia driver problem.
First thing to remember is that my system i.e. mandrake 9.1 install, is a power pack dvd workstation version.
As far as I can tell, this is what may have caused my confusion. Because my system already had an older version of the nvidia driver, that had been installed as a kernel module when I installed the system.
As I wasn't aware that this would make any difference, I just followed the mandrake 9.1 Nvidia driver install which seems to live at the LinuxAnswers section.
This meant that my X server wouldn't start. And even though I'd made sure that my /etc/X11/XF86Config-4 file was correct (well, as per the instructions), The x server still didn't want to start.
The 2 things that seem to have confused me, was the older kernel module for the earlier nvidia driver version, and in my /etc/X11/XF86Config-4, instead of having the line in the module section that should have said Load "glx" there was one that said something about /usr/share/x11*************(can't recall the middle bit)/libglx.so which I'm presuming was the location of the library for the glx - which the nvidia-installer uninstalled (the glx module, that is).
So all I have had to do, in the end, was remove the old kernel module, make sure that my xf86config file was as per the instructions (oh, not to forget to change the /usr/share*************whatever/libglx.so line to just Load "glx") and then just put the /etc/inittab back to level 5 for graphic startup.
This seems to have worked for me - hope it may help someone else ??
p.s. Oh and when it comes to changing you XF86Config-4 and /etc/inittab, you can do that by just putting vi /etc/X11/XF86Config-4 and the same for /etc/inittab - but if like me, you've not used vi (or vim) for editing, dig around and get the basic instructions for the commands so that you know shit like :wq is what's needed to save and quit.