Well I was trying to upgrade the CPU in my kids' Dell Optiplex 380, it had a Pentium E5300 (dual core 2.6GHz), I couldn't decide if I wanted more cores, or faster cores, I didn't want to spend $80 for both. I thought it was unfortunate that I won a C2D E8500 and C2Q Q8400 on eBay, both for cheap. But I put the Quad in and it only shows two cores? Perhaps a motherboard limitation? But the spec sheet said this CPU was supported. I put the Duo in and will keep it 2 cores but much faster than the Pentium cores, with more cache as well. I'm not sure if this crappy Dell heatsink could handle 4 cores and 95w anyway. I guess I will be listing the Q8400 as I can't use it. At least I can probably get my money back and possible a dollar or two in profit.