Here's the poop from BIOS:
After a quick go 'round with the universal driver again, the system would not take any setting beyond 640 X 480 @ 4 bits.
AGP Aperture: 32mB
Onboard Video Buffer: 1mB
Dunno what to say here, other than it's a reasonably new crappy Dell with all of the usual quick-and-dirty tricks which they build into them...
The standard 82865G Graphics Controller shows that it's running on a full 92mB of video memory. Apparently the universal driver can't access most of this (?)
I've uploaded a shot of the display applet to tell the tale --