Syntax sv266a/amd 2400 problems

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I purchased a syntax mbo combo with an amd 2400 proc. I installed the motherboard/new ram/new proc.. To my dismay, everything along the back of the board did not work such as keyboard, mouse, usb ect. But the fans/LED worked fine. I assumed it was a defective mobo, so i returned it and picked up another one. I got home, installed the new proc. and the same problem. So, I contacted syntax and they said it sounded like there wasn't enough power to the board, so i replaced my 300w power supply with a 400w. Still the same problem. I am stuck, I don't know where to go from here!! Has anyone encountered a similiar problem? I think it might be the processor. I even tested different compatible RAM. Please help!!