I don't know which version of Catalyst I have on my HTPC, but here's how to set up multiple monitors (make sure both monitor and TV are connected and powered on):
1. Right click the desktop and choose Properties
2. Click the Settings Table
3. Click the Advanced button
4. You should have 3 rows of tabs to choose from, click Displays
The new window should show 4 different displays. One is your monitor, another is the TV. If the TV has a button that is red, click it and it will change to a bluish green. The button for your monitor will change from grey to bluish green as well.
Note that each monitor will have two buttons to click on. By default the monitor will have the left button clicked because it is the primary display. The TV will have the right button clicked by default. This is the extended desktop or secondary display. Click the left button to make it the primary display so whatever your monitor displays, the TV will display as well.