Windows 7 X64 Ultimate Using Only One Core Of T5600 Core 2 Duo

I'm having is that I recently installed Windows 7 Ultimate (from XP Ultimate) and the computer was working really slowly.

First I opened task manager and found only one CPU was being monitored, there was only one window for one CPU, not two windows with only one firing!

This I found strange, checked the WEI and my processor got a 2.3 rating (its a Core 2 Duo @ 1,83Mhz, a T5600), I then downloaded a tone of widgets to check if they could "see" the other core, nothing. I went into msconfig, the no. of processors box is unchecked, if I check it, the drop down menu only gives me the option of picking 1 CPU.

using Vista, but I can't seem to be able to use his fix: [URL] (bottom of page, can't find the HAL detection checkbox)

I am running Windows 7 Ultimate on an HP nx9420 laptop with 3GB of RAM, a new HDD (250GB), the old one just stopped working really, and the Core 2 Duo T5600 @ 1,83Mhz that is running only one core.