OK, CPU-Z says chipset is E946GZ, CPU Pentium D935, BIOS Phoenix 2007.

From memory isn't there a bios setting for which display gets initiated first?  If a secondary display isn't detected there it defaults to the on board graphics.  You need to set it before installing the new card.

Thanks everyone for the help and tips. I was eventually able to get this working with a lot of fiddling and some BIOS adjustments. I think there was a hardware issue amongst other things, due to the age and dirtiness of the items. Eventually the card just started working. I still do have to change the BIOS setting to choose between VGA and DVI. I can get either one to display but I can’t get them to display together. Is this possible with this BIOS?

The VGA settings are Auto, On chip and Peg port. Auto selects the DVI monitor when both are connected. On chip selects VGA. Peg port makes it go crazy and start producing error beeps. It also wiped out my boot sector, requiring a repair operation. 

What I have now is acceptable. It just means I have to go into the BIOS to change the monitor. It would be ideal if I could get both monitors to just work together so whichever one is plugged in displays.

Rikkitic:

 

What I have now is acceptable. It just means I have to go into the BIOS to change the monitor. It would be ideal if I could get both monitors to just work together so whichever one is plugged in displays.

 

So this means the person needs to have both types of monitors available, in case the external one dies and you need to update the BIOS?

What I hoped to achieve was two working monitor ports, one VGA and one DVI, so either monitor type could be used by simply plugging it into the port. I would give the kid a working VGA monitor, but if it ever died or he wanted something better, he could just plug in a DVI/HDMI monitor and it would work without any further action necessary. Where I am right now is both display types work, but I have to keep changing a BIOS setting to switch from one to the other. 

Edit: I just saw what you mean. If the monitor in use fails, he can't see to switch to the other one. Hmmm...

I haven't seen anything like that and I don't think it exists but I will keep looking. This Acer BIOS does date from 2007 but that shouldn't be an issue. Maybe there is a malfunction.

I went through it all again and can't find anything that works. So instead I came up with a half-arsed solution that allows me to move on to real problems. 

I have a lot of old stuff collected over the years. I'm actually surprised at how many graphics cards I have. Anyway, I found one with both VGA and HDMI on board. Plugged it in, connected the monitors and voila! both work. That's it. I'm done. The kid can just plug in whatever he wants.