Catalyst 10.7 + 3 monitors in SurroundView
This is my guide to setting up triple screens with Xubuntu 10.04 desktop i386 (I have also tested this with Mint 9 Isadora - Ubuntu Lucid 10.04).
Please read all of my previous posts on this page regarding the now outdated Xubuntu Intrepid 8.10.
The method is the same as before but updated here for 10.04 - so if you get stuck please refer to my previous posts (#17 is most relevant).

1. Make sure you have the correct ATI hardware.
Check that the onboard graphics chipset and the plugin-card graphics chipset are both from the same series (3200 for example).
I use a Sapphire Pure Hybrid Crossfire PI-AM2RS780G motherboard and an HD3450 fanless graphics card. So this is 18 months old and budget range.
You will be able to connect 4 screens to your computer, providing one big desktop, or any other configuration possible with ATI Catalyst.
If you want to do gaming then use a faster more powerful motherboard and graphics card and an adequate power supply.

2. Download and burn to cd and install xubuntu-10.04-desktop-i386.iso, then do the latest updates.
I would advise at this stage, until the graphics is set up, not to start trimming and tweaking your distribution - so keep it pristine for now.

If at this stage you have not been alerted by the Jockey (hardware drivers) prompt from your notification area (system tray) that new hardware drivers are available, then you need to go to (xfce menu) Applications, System, Hardware Drivers and Jockey will search for drivers and recommend ATI/AMD proprietary FGLRX graphics driver.

At the time of writing July 28th 2010, the Jockey recommended driver did not work on my system with 3 screens.
So I then tried reinstalling Xubuntu and this time I ignored the Jockey recommendation and went straight for the ati-driver-installer-10.7 available directly from AMD/ATI.
In both cases there were all sorts of problems (which I solved below), these problems usually occured right at the finish after re-enabling surround view in the BIOS and after adding the 3rd or 4th monitors in Catalyst.

The solution for the time being (until the Xubuntu repos are updated) is to do an Xubuntu pristine install, latest updates then install the Jockey recommended hardware drivers.
Then go to Synaptic Package Manager and remove the installed packages fglrx and fglrx-amdcccle and only remove those two and no others.

On my system it seems that doing the Jockey recommended install of fglrx paved the way for a trouble free install of the ati-driver-installer-10-7-x86.x86_64.run (see below).
Failing to do the jockey recommended install first and then fglrx and fglrx-amdcccle removal in Synaptic always resulted in my ati-driver-installer-10-7-x86.x86_64.run failing.

Having done the 'fglrx dance' described above, now download and install ati-driver-installer-10-7-x86.x86_64.run from AMD/ATI.
Execute the file using a terminal (available from the xfce menu). become root user (sudo su), navigate to the folder containing the .run (cd ..) or open a root terminal in the containing folder.
# chmod +x ati-driver-installer-10-7-x86.x86_64.run
# ./ati-driver-installer-10-7-x86.x86_64.run
Alternatively you could open the containing folder as 'root user' (thunar custom action, gksudo thunar, appearance condition 'Directories') and then simply double click the .run file and see if the Installer starts.
Once Catalyst has installed you might need to create your own launcher (command gksudo amdcccle).
Launch Catalyst and setup two screens.
I don't want to repeat myself here so please refer to my previous posts #17, #19 and #20 for further information. #17 is the most relevant.
Key points are:
1. To get the 3rd and 4th screens re-enable surround view in the BIOS.
2. Use aticonfig in console mode if your graphics fails to start.
3. Use a hot pluggable USB keyboard and USB mouse (or cheaply adapt PS2 to become USB) which will recover from 'lockups' where PS2 stubbornly refuses to.

Xubuntu + Lucid 10.04 + ATI/AMD Catalyst 10.7 + 3 (or 4) monitors in SurroundView.
I am once again extremely happy with my setup of three 22inch screens.
I did upgrade my 'single screen friends and family' to Lucid 10.04 back in April, but couldn't get 4 screens to work with the new release.
That problem and an intensely annoying bug with Thunar, in which the file manager detailed view froze up (which is now fixed), prevented me from upgrading and I stayed with Jaunty 9.04 until yesterday.
Thanks to all the developers who made this possible.
The setup I described here is being used for web design tasks only and is fine for that.
I use another identical computer with only one screen and Mint 9 for multimedia tasks such as viewing video files and on that I have noticed slight tearing of the video.
That problem and very similar ones are being discussed on other internet threads.
Looking to the near future - hopefully the 'fglrx dance' I described above will get fixed and won't be necessary.
I am very impressed with my hardware, Lucid Lynx (Xubuntu) and ATI/AMD Catalyst 10.7 - everything I want (for daily routine productivity tasks) seems to work.

Kevin Dixon