General Procedure to get ATI/DRI card running?

[Labitt, Bruce]

I just got an ATI/AMD Radeon X1650 Pro video card to try to replace the
onboard video on a Dell Optiplex 745 running Scientific Linux 5.1.

So I just plugged the Radeon in and started the computer.  Um, during
boot it said - "Oh no, you don't want to do that... You've got too many
video sources for your monitor... Unplug one and start over."  So I did.
Everything was fine until the OS tried to start X.  Then everything
died.  I got a couple of options to look at.  An error message came up
and said it could not find a video card.  Of course, I don't know how I
could have read anything on the screen, if it did not find the card, but
I digress.  It said I could fix things if I were root, so I dutifully
complied.  As soon as I became root it tried and failed to start x.  It
then said, "hey, I'm brilliant, why don't I probe stuff and generate a
new x.conf file?"  The screen turned pretty colors for a while and
eventually froze.  After a while, (many minutes) I reset the computer.

So I currently have xorg-x11-server 1.1-48.41.el5-2.1

What do I need to do to 1) get X to even start. 2) run 2D 3) run 3D.
The computer is back to running on the intel chipset for now.

Do I need to update the above file?  There does not appear to be an
update in the repository.  I don't mind compiling stuff, having compiled
octave, lapack, blas, and a few other packages.  However, having not
done this adventure before (os video) I don't know what the order of
steps should be.  

There was nothing on the SL site on video upgrades, although they did
have proprietary drivers with no instructions on how to install.

I'd like to go with OS / DRI if at all possible.

Without belaboring this further, a couple of steps, or a general
procedure would be greatly appreciated.

Thanks,
-Bruce