Can't figure out how to make this query

[MR ZenWiz]

I just changed my motherboard and the new video controller is an ATI
RADEON, but I was using NVidia before.

Without re-installing Ubuntu, what do I need to do to change the
initrd (and xorg.conf) so that it will come up with the right video
configuration?

OR

Is there a generic way to do this without the specific controller
driver (which I could set after rebooting)?

I tried about four ways to google this and none of them worked right
(I can be a google-klutz at times).

Soonest response possible would be highly appreciated.

(Ric, are you out there?  I just know you'll also have some good
advice on how to re-enable PulseAudio, which might work with the new
m/b controller....)

I am currently booted from the live CD, but that won't make it for
long - I want my file systems back....

I keep thinking that this is really easy, but hanged if I can remember
it (will record for future such issues....)