To install the video drivers from source you'll have to download the kernel headers, or install a custom kernel. See secion Installing Custom kernel.
To do this process I'm creating a directory in mythtv's home directory (/home/mythtv) called nvidia, then going into that directory and downloading the nvidia drivers with the wget command. Then I switch to mode 3, and perform the installation of the driver.
This process involves the creation of a kernel module, meaning that everytime the kernel version changes (when doing a #yum update), you'll have to do it again.
Once the module is built, switch back to run mode 5.
These are the commands to perform all that:
Now you can save your /etc/X11/xorg.conf and download my working xorg.conf. In case it doesn't work for you, you can always return to your previous xorf.conf or try the graphic configuration (see below).
To go back to praphics mode do:
Once you are back in KDE, you can configure your graphics adapter by going to:
System->NVIDIA X Server Settings