Here is what I have:
Intel DG31PR and a E8400 CPU.
I noticed that only 1 core was being used and that the performance tab in Task manager in Windows XP only showed one graph. I ran CPUz to confirm and it stated only 1 core used. I checked in the device drivers and sure enough under the Computer branch only Standard PC was listed.
I then reinstalled Windows XP and kept pressing F5 to get to the HAL choice menu during installation. In this menu ONLY Standard PC with C-step I486 was listed and other. I chose standard since other gave me no options.
I installed XP, installed the latest board drivers:
I checked my BIOS, it is the latest version:
No matter what I tried I cannot get the dual core to work or the ACPMI to install in the drivers. I tried replacing hal.dll and kernel files with the relevant files for ACPMI and it bluescreened me on bootup every time.
Currently I am stuck and cannot find a solution as to why I cannot use both cores on my CPU.