X configuration problem.

I have a PC that came with Windows 2000 installed
with an AGP video card. The BIOS spells AGP
everywhere.
I changed whatever I could to PCI, but PnP is still
there because the alternative would ISA-EISA, which
I don't think is correct.
After installing the Seawolf distribution in a
separate
hard drive, I could not get graphics on screen.
The only graphics that I could display was less than
640x480 pixels, which are not enough for my purposes.

I am now trying a regular ATI Mach64 board with 2 MB
memory. When I try xinit, it crashes with messages
to the effect that the board does not support 16 bits
color. When I define 8 bit only at any screen
resolution, the signal simply goes out (the LED on
the monitor front lights yellow).
I tried the hardware with a preinstalled Windows 98
disk which, after loading lots of drivers, works
fine.
I tried the lowest resolutions and memory settings
but the result is always the same: a totally dark
screen under Linux.
This is a new hardware problem. I need suggestions
on how to proceed.
Thank you.

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