T3-P5G965 Intel GMA & Vista Ultimate problem

Hi All,

I own an Asus barebone T3-P5G965 (Intel G965 Express Chipset) with
Pentium Dual Core 2160 and 1Gb DDR2@667MHz RAM, till few days ago with
XP SP2 OS. Upgrading the hard-disk I decided to upgrade also the OS to
Vista Ultimate 64bit.

All works perfectly, except the video drivers:
- from Intel web site I downloaded and installed the chipset INF upgrade
- from Intel web site I downloaded and installed the video driver for
Intel GMA, the only one available now: 15.6.1 for Vista 64 bit

Once installed, the system cannot upgrade the Hardware sco the igfx
driver stop to respond, the screen turns black, then the OS recovers it
and an annoying pop-up with a brief description of this error is displayed.
I can't even activate Aero, in particular with transparency activated,
because I get a lot of the above errors.
The only problem in device management is an unrecognized PCI simple bus,
which I don't really know what it is related to.
With Windows XP I didn't had any problems with video driver, the test I
did, even with 3D Mark'06, worked perfectly.

PS: the Asus programs & drivers contained in bundled CD or downloadable
from the official web site don't work. It seems they are not intended to
be used with this OS version.

PPS: after all this I tried also to upgrade the motherboard BIOS to
latest version and install Vista Ultimate 32bit, in both cases I
obtained the same error described above.

Thanks in advance,
rJ.