As I remember, all the time, after fresh-installing Ubuntu on my HP ProBook 4530s, the Radeon graphics doesn't work, it uses Intel Sandybridge Mobile instead. The point is, that the required driver packages are already installed, but system uses the Intel driver anyway.

Driver packages installed:
xserver-xorg-video-ati xserver-xorg-video-radeon xserver-xorg-video-vesa xserver-xorg-video-intel xserver-xorg-video-all
I was using the proprietary Catalyst driver until today and it was very buggy! Many GTK apps were crashing, Compiz was crashing, even session was crashing when trying to switch account from user menu, selecting brush in MyPaint or dragging image from eog. I decided to remove this proprietary s*** and use open-source radeon driver instead. After quick googling I found this Ubuntu community Wiki-article, followed it but only Intel driver was being used...
$ glxinfo
OpenGL vendor string: Tungsten Graphics, Inc
OpenGL renderer string: Mesa DRI Intel(R) Sandybridge Mobile 
OpenGL version string: 3.0 Mesa 8.0.2
OpenGL shading language version string: 1.30
OpenGL extensions:
I also read this guide but didn't helped. After about 3 hour searching the internet and trying some xorg configs, I didn't found useful information. But, then I tried to do a little hack:
# mv /usr/lib/x86_64-linux-gnu/dri/ /usr/lib/x86_64-linux-gnu/dri/
# ln -s /usr/lib/x86_64-linux-gnu/dri/ /usr/lib/x86_64-linux-gnu/dri/
And I got:
OpenGL vendor string: VMware, Inc.
OpenGL renderer string: Gallium 0.4 on llvmpipe (LLVM 0x300)
OpenGL version string: 2.1 Mesa 8.0.2
OpenGL shading language version string: 1.20
OpenGL extensions:
After restarting computer, Radeon graphics started working, but only Unity-2d session was loaded. It's clear, that configuring xorg is necessary, but what's wrong with radeon driver?!
Please help to solve the problem, I really don't want to go back to FGLRX driver