This could also work with other Linux distributions. Afaik Scientific
linux is based on RedHat.
1. Download NVidia driver
2. open: /boot/grub/grub.conf :
add rdblacklist=nouveau to the end of the kernel line
3. reboot
4. At startup go to the grub command line(s) and add to the end of the kernel line " single" to boot to runlevel 1.
This change is not permanent.
5. Once you are in, enter init 3 to switch to runlevel 3
6. Type sh NVIDIAxxx.run to start the installation