Intel Motherboard won't boot, no keyboard / display detected

Hi, I'm new here, and a novice to building new PC's from scratch, wondering if you guys could help me here.
I'm trying to get my motherboard to post, testing it outside of PC case with just processor, 1 stick of memory, and a video card. If i remove the memory it does its normal 3 beeps..
My mobo is Intel DP45SG http://www.intel.com/products/desk [...] erview.htm
CPU: Intel Core 2 Duo http://www.newegg.com/Product/Prod [...] 6819115036
Memory: 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666) http://www.newegg.com/Product/Prod [...] 6820227336
Video Card: Geforce 9800 GTX http://www.nvidia.com/object/geforce_9800gtx.html

I have test it with 2 different power supplies, 2 different DP45SG motherboards, another regular old PCI video card, 2 different monitors.. and by testing all this multiple times I rulled out everything except processor, memory and video card compatability. Was quite unsure about memory cuz mobo guide says it needs non-ecc and unbuffered memory.

So my motherboard responds when i put no memory in, power is connected properly, BUT nothing on the keyboard or monitor happens..

If anyone has free time, could someone please give me a hand in resolving this issue, thanks in advance.

If nothing will come up but the fan spins than check your memory first try re-seating it first only one ram at a time in diffrent slots than if no boot than try a diffrent ram all together and if still no boot than check your cpu it may need to be replaced. Good luck. If no post and your board is working than it is your cpu or memory.