ati's multimonitor software is called hydravision... use that for most of your needs but I recommend an app like ultramon (please google am in class... can't do it right now) that will allow you to span the taskbar and gives you better overall control over both monitors and what is displayed...
I could never find the hydravision options for different wallpapers on different screens so I got ultramon on sazar's recommendation, pretty damned good if you ask me - you have to register it if you like it enoug to keep it though.
this program is awesome. this s directly from the site.
UltraMon is a utility for multi-monitor systems, designed to increase productivity and unlock the full potential of multiple monitors.
efficiently move windows and maximize windows across the desktop
manage more applications with the Smart Taskbar
control application positioning with UltraMon Shortcuts
multi-monitor support for desktop wallpapers and screen savers
mirror your main monitor to secondary monitors for a presentation]
i think it has a free tour. i personaly think its worth the money but i use dual alot.
... I use basic, unmodified Catalyst 4.1 drivers (doesnt matter what version you use) and a Radeon 9600xt... its pretty simple to use two different wallpapers(or one large one), all you have to do is make an HTML file with the two images beside one another(or just the single large one), and set that as the background - with that, ultramon and hydravision can do almost the same stuff
 as for the start bar that spans both monitors, I just made a fake bar as part of the background image, look here, so it doesnt take too much[/edit]