Intel GMA T3-P5G965 & 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 score: 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.