HP nx9420, Nvida fx 1500m not working after upgrade

[YesMan]

Greetings!

I need help and advice on how to get my machine up and running.
I've searched for solutions, those I have tried makes my machine worse!

System Model
Hewlett-Packard HP Compaq nx9420 (RH446EA#A2M) F.1D


Main Circuit Board
Board: Hewlett-Packard 309F KBC Version 54.3D
Bus Clock: 166 megahertz
BIOS: Hewlett-Packard 68YAF Ver. F.1D 07/11/2008

Intel Core Duo processor T7200
http://ark.intel.com/products/27255?wapkw=t7200

All versions of the nx9420 model
Mine is (RH446EA#A2M) but with Intel T7200 processor


I did a clean win8 64bit install. It was running just fine on w7 32bit without any
changes to bios or modifications other than the normal updates offered by
windows.

I need the full use of 4GB RAM, I only have access to 3,4GB
I read somewhere the intel chipset will not support more than 3,4GB?

Before I installed w8 I upgraded the CPU, after install the new Nvida fx1500m is not
listed in Device Manger, I downloaded the original and latest vista 64bit drivers (2008)
from HP for nw9440 and after installing the drivers, rebooted the machine and now I
get a blank screen where I can move the mouse around and that's it and I had to
restore my machine.

To my best of knowledge the nx9420 bios (D 1. 14) will not support my new CPU so
I updated the bios, I followed all given info on HP site and I went for the nw9440
bios (F.1D) as this CPU came with the nw9440 model but, it quit the install "the bios
your are installing is older than the one already installed" don't know why as the
nw9440 is a newer and upgraded model of the nx9420 and for some reasons, the
new BIOS is listed as installed when the fact is, it is not installed! When I boot up and
go into the bios, the original bios version is still listed.

More info on HP nw9440

I am hoping someone can tell me what I need to do and where I can get what I
need to get my machine up and running ASAP!

Also, I want to upgrade my WIFI to N, found a driver that should work but the install
refuse to install this driver, any ideas?

Thanks in advance

Dennis