It depends what you want to do with this computer. If you're just doing some simple internet the open source drivers coming with your package manager will suffice.
When gaming / video editing is important, the proprietrary drivers are needed. At the NVIDIA site the most recent drivers can be downloaded by clicking Download drivers >> Beta and archived drivers and after choosing the 8 series, 8400 model a list of drivers will appear. Choose the highest version (about 256.35) and click [download], and then right-click on the [Agree and download] button (most browsers will open it as a text file when using the left button) and choose [Save as...] in the list.
Now the file is on your disk, make sure you got the standard NVIDIA drivers installed with GLX in your package manager (The proprietrary driver overwrites some binary files of the originally installed drivers to make it work). Also make sure packages like linux-headers (your kernel version), dkms, automake, autoconf, module-assistant, g++, mesa-utils are installed on your machine.
Now we need to switch to runlevel 3 (I think Fedora Core uses runlevel 3). Just log off your profile until you're at the login screen. Now switch to a text console, by pressing [Ctrl]-[Alt]-[F1] (F keys 1-6 are all text consoles)
As sudoer the easiest way to become root is:
Type the following in the console:
Now the machine will close the graphical interface and it will ask for the root password (or if you're a sudoer your own password) and after entering it you're logged in again in a text console.
Go to the directory where you downloaded the NVIDIA driver and run the file:
Or the other filename if you've got a 64bit version of your kernel.
Now the script will ask you a few questions. If it's moaning about an X still running, try to repeat the part above with the init, lowering the number with 1 each time. Even if the script will ask you to abort with a slight difference in GCC version or warns you about some alterings, just tell it to go on and let it compile the new module. Since it's the first time to compile this NVIDIA module, accept the offer to let it configure your X settings. If it offers this configuring, there's a good chance the new drivers will work correctly.
Now the driver is installed, you may start on the fly by entering:
Or restart the entire system to see how it boots:
When the graphical interface returns, log in and open an xterm (or your favourite X console) window, and type the following command:
If everything works fine, 3 gears are rotating and in the console window the number of frames per second will be measured. This value should be 4000 or above with the video card you have.
I must warn you: installing the proprietrary drivers sometimes fails and can't be undone, only restoring a backup or re-installing is an option then. So make a backup first if you're working with a live system.