I had been trying to get the drivers from ATI working for several months now. Recently I decided to give it another try. I did a fresh install of Debian Etch, only a base system. I am using the amd64 arch, but everything should work for the other archs as well. I did an apt-get install gnome xorg. That is all I had before I began following several guides until I got it working with the below steps. Also I did all this as root so you may need to install fakeroot or something along those lines.
First grab some dependencies
apt-get install module-assistant build-essential dh-make debhelper debconf libstdc++5 linux-headers-$(uname -r)
Then I downloaded the drivers from: http://ati.amd.com/support/driver.html
(Select either Linux_x86 or Linux_x86_64, then Integrated/Motherboard, then Radeon Xpress 200)
After that make sure the driver is executable and then have it build the .debs:
./ati-driver-installer-8.32.5-x86.x86_64.run --buildpkg Debian/etch
Then install the debs:
Then add this to /etc/X11/xorg.conf at the end:
Option "Composite" "Disable"
Then compile the driver:
m-a a-i fglrx
Then finally have the driver setup the rest of your xorg.conf file automatically:
Then reboot and everything should be all set.
I'm a tad new at this so I will try to answer any questions and I hope this helps.