Ok, here is where you need to troubleshoot. You can easily test the PSU with a multimeter. They are pretty cheap. See if the 12v rail is pulling 12 volts. i had the same problem with one of my systems and the system started but would not boot to windows. i changed every piece of hardware and then tested the 12V rail and bingo. 8 volts.
It could be a drive, bad sata cable, memory ect........ Bottom line is: board works.
So far, everyone is crapshooting. if you do it in order, you will find the problem.
Here is a tutoral on testing PSU
Manually Test a (PSU) Power Supply With a Multimet...