Ubuntu 13.10 now supports Hybrid Graphics. If you have Ubuntu 13.10 and Radeon hybrid graphics you can install the driver and catalyst control center as easy as follows:
sudo apt-get install fglrx fglrx-pxpress
Then your fan problem and driver issues will be gone. And after you can start Catalyst Control Center and switch your graphics card. You can start catalyst control center in dash by shortcut or through terminal as follows:
--remember to run Catalyst Control Center as root to switch graphics--
I really don't know whether above works with Ubuntu 13.04 or earlier. For those old systems you can just turn off the discrete graphics card (ATI Radeon Graphics card) to solve overheating, fan issue and increase battery life.
You can just turn off ATI card as follows:
chmod -R 705 /sys/kernel/debug
chown -R $USER: /sys/kernel/debug/vgaswitcheroo
echo OFF > /sys/kernel/debug/vgaswitcheroo/switch
You can then add the 3rd command into /etc/rc.local file before exit() command so that it executes everytime when system starts. This also worked for me in Ubuntu 13.04.