Gigabyte ga-7n400Pro2 rev.1 - GART Driver doesn't work fine - Unable to active AGP-8X!!

Hello, i'va a Gigabyte 7n400Pro2 - Rev.1 (bios F11)
i've installed XP Professional, SP1 & SP2 then i begun to install the
gigabyte mainboard drivers.
When i install the GART Driver (AGP Controller driver) and i reboot the PC,
the boot screen appears and all seem to work good, but after few seconds,
before
the blue login screen, the monitor goes blank and the monitor's green led
become yellow, the system doesn't continue booting.
I've found that there are some problem with the GART driver, and i know that
ONLY this driver(present in the Nvidia Driver Package and in Nvidia Omega
Driver package)
can use AGP8X mode efficiently.
I've fixed the blank screen problem using the AGP controller drivers
(present on the Windows XP
Professional installation CD) but with these drivers i work ONLY in AGP-4X
mode.
I know that AGP-8X mode is able because i've tested the mainboard with
Sandra 2005.
So i'd like some suggestion.
The VGA-card is Nvidia Geforce-4 MX440 128Mb with fully AGP-8X support.

Sincerely TheSirac