Rebuilt System not working.

My friend recently bought a new case for his computer, we took the parts out of his old case and put them in his new case. I made sure I had all the parts installed properly. The computer turns on but it never actually boots. Its getting power, all the case fans are running, the light on the mobo is on. What could be wrong?

I'd also consider whether you used same PSU or a new one.

If everything is the same maybe you have the power switch on the mobo wrong or check all the cables/cards/ram something may not be in right.