multiple monitors - ATI graphics card overriding onboard Intel graphics

I have an ATI graphics card with an AGP connection and a DVI port, and an Intel graphics processor on the motherboard with a VGA port. I have two monitors.

When the graphics card is unplugged, I get this from lspci:

00:00.0 Host bridge: Intel Corporation 82G33/G31/P35/P31 Express DRAM Controller (rev 10)

00:02.0 VGA compatible controller: Intel Corporation 82G33/G31 Express Integrated Graphics Controller (rev 10)

When it is attached, I get this:

00:00.0 Host bridge: Intel Corporation 82G33/G31/P35/P31 Express DRAM Controller (rev 10)

01:00.0 VGA compatible controller: ATI Technologies Inc RV380 [Radeon X600 (PCIE)]

01:00.1 Display controller: ATI Technologies Inc RV380 [Radeon X600]

Note the absence of 00:02.0 - this is apparently causing the VGA monitor to say "No Signal" and the only the DVI display to show up in the list.

I checked for problems in xorg.conf... there isn't one. I have no idea how to build one.

All I can recommend is: Check your BIOS.

If it's not showing up in lspci, the problem is way above X's jurisdiction. It could be kernel related but logically speaking, this sounds like a power-saving "feature" on the motherboard.

Check through the settings in the BIOS and see if you can see anything to do with the onboard graphics. If it's set to something fuzzy like "Auto", change it to something more assertive like "Enabled".

Or buy a new card with both outputs on the one card. As AGP is dying out, they're quire easy to pick up second hand, dirt cheap. Leave it much longer and they'll start going up as they get rarer.