Its just a guess Jorge,
Im not at all sure it will work/help. Have you verified that you have the latest drivers for the monitors as well? You didnt list the monitor so I dont know about them. Can you find out?
You can get 256 color without the proper drivers for the card, that is the way win2k starts - with the default vga driver. The default vga driver is a generic driver that allows all the win OS's to run either in safe mode or regularly until the proper drivers for the card and monitors are installed.
Vern