Hello,well lets see whats happening.
This is a brand new build?
Ok you have connected 24 pin power supply and the seprate 4 pin power supply to mainboard located left of the
CPU?
Does this computer power up?
Are all the fans spinning?
Do your CD/DVD rom drives seem to get power?
Check all connections are correct.
If yes?
Try this:
Power off computer now turn on and quickly insert operating install disk see if it starts to install the OS.
If you are using a USB keyboard/mouse can you use a PS2 set?