What Catalyst version are you using? What windows version are you using?
I'll assume Cat 10.x and Windows 7.
Go to CCC>Graphics>Desktop & Displays
Under "Please select a display", you should see two display icons. 1, your LCD TV and 2, your LCD monitor.
On your LCD monitor icon, click on the black triangle and select "make preferred".
Alternatively, right click on your desktop and choose "Screen resolution".
Under "Display" Select 1|2 Multiple Monitors.
Under "Multiple Displays" select "Duplicate these Displays".