Computer only recognizes 1 core for C2D

I have an E8500 C2D cpu on a Asus P5K/EPU motherboard with 2gb ddr2-800 ram. The problem is that windows AND the BIOS of the motherboard only recognize one core (core count = 1 in bios) (cpu-z = 1 core, 1 thread, and Bus speed/HT Link not shown/greyed out). Im just wonder if any1 has any solutions/suggestions on how to fix this and whether or not my motherboard is just screwed up, because however I remember that it USED to say that it had 2 cores but suddenly one day I was looking at my "all cpu meter" from the vista gadgets and Core 2 was at 0% which made me look into it further.

have u tryed updating bios

Download this and run it... see the cpu and run the benchmark...

http://www.techpowerup.com/downloads/SysInfo/Everest/

i downloaded it, ran the cache/memory benchmark and here were the results, but even then, under motherboard - cpu - cpu utilization, it only shows one core being active.

http://photos-e.ak.facebook.com/photos-ak-snc1/v350/75/121/509234613/n509234613_815868_5269.jpg

http://photos-f.ak.facebook.com/photos-ak-snc1/v350/75/121/509234613/n509234613_815869_7401.jpg