OK, I went back through the forums and found how to mount the floppy. I did the following:
mount /dev/fd0 /mnt/floppy
rpm -i nvid.rpm
I then rebooted after unmounting the floppy, and a screen came up asking me to configure the graphics card by inputting IP adresses. My computer isn't on the internet, so I just made up an IP address on the spot. After this had finished, Linux carried on booting up as before, and still comes up with a blank screen after the login screen.
So now I am totally stuck. Please help! ??? >