I've been using Windows XP's Extended Desktop mode with a projector + a PC (with a dual-head video card) or laptop for years.
Now I have an old HP Evo D5S running WinXP Pro which has onboard video (Intel 82845G/GL/GE/PE/GV), so there is just one VGA output. If I go into Display Properties > Settings, I can see just one screen, as expected.
Now, if I install a separate video card (ATI Rageon 7500 Series AGP, which has one VGA and one S-video output), and go into Display Properties > Settings, then I see a picture of 2 screens (numered "1" and "2"). (Note that I had to swap my screen from the onboard to the card's VGA port, otherwise I get no signal).
I'll number my questions:
1. Would it be true to say that if we can see 2 screens under Display Properties > Settings, then the system has all the hardware that is required to handle Extended Desktop mode?
2. If so, why could it be that when I connect a 2nd monitor to the onboard video VGA port, and turn it on, and check the "Extend my Windows desktop onto this monitor" box for screen "2" under Display Properties > Settings, the primary screen just goes blank for a few secs, then comes back, but the "Extend my..." box reverts to unchecked, and it's definitely no longer in Extended Desktop mode? (Considering the high resolution options, I doubt that the screen "2" relates to the S-video port of the card).
3. To use Extended Desktop mode, is it really necessary to have a dual-head card for a desktop PC, or can it be done with an onboard card (with one VGA port) plus a graphics card (with another VGA port), like I have?
Please number your answers accordingly, even if you're not answering all my questions.