A driver not found error usually means that he isn't in the car, so just go find him.
ANYWAY...you have 2 problems which have the same solution.
1. You need a kernel 2.6.19 or higher because, your IDE controller isn't being recognized. You'll need to enable the new libata settings though ("Marvell PATA" controller).
2. You can't use X when installing unless you have a 2.6.19 kernel (which is why you are probably getting the ugly install screen--most likely some primitive framebuffer), because you need a some of the newer features in AGPGART which are only available from > 2.6.19.
So installation is probably going to be tricky. If the newest install DVD has kernel 2.6.19 they you are in luck. Otherwise you are probably going to have to install in text mode via http/ftp (or you local hard drive but that's a pain), then download, compile, and install a new kernel.
As to why your DVD drive boots, it is a bit of a chicken/egg problem relating to IDE controllers. Your drive can boot and do some stuff, but it needs some more information from a driver to be able to do anything else. (Just a guess, we're not that far in computer architecture yet