G4 800MHZ vga main display?

This is my first time posting a question. I have a Power mac G4 800MHZ. I want to hook it up to my new Samsung LCD but when I use the vga port my computer thinks I want to see dual monitors instead of the vga being the only monitor. The other port is the ADC port.
I have no idea what to do at this point.....I've tried everything and am stumped....Please help if anyone knows.
Thanks

i believe if you go to you System Preferences>Displays, you can turn on "Monitor Mirroring". Or click "Detect Displays" and see what happens.

I tried doing the monitor mirror but then when I try to go full screen with a quicktime video it gets confused and thinks I want to go full screen with both monitors......Also when I shut the computer off and turn it back on the tv will work on the log in screen and then all of a sudden the tv will say mode not supported. So then I shut it back down and hook up the adc so now the tv and apple display are hooked up and the tv works fine.