reset cmos then try.
if not time to hook up only the bare minimum. do you have an onboard monitor port?
try that first, if not. unplug everything except one stick of ram, the gpu, and heatsink fan, and your swpower.
try switching ram around.
if not,
take mobo out, put it on a static bag, hook up only your gpu, 1 stick of ram, heatsink fan, plug it to the psu and jumpstart with a small screw driver touching the two sw power pins. don't forget to plug in your monitor.
could be your mobo is grounded out.
if it still don't post you've narrowed it down to, cpu, gpu, psu, and mobo.
if your cpu is the same socket as your other system try it in there.
try using your other psu.
good luck