set it up out of case where you can get a good look at everything
set it up out of the case on a piece of cardboard with
cpu
video
ram
speaker
and see if you get post
check you have the correct amount of standoffs no more no less
that they line up with the holes in the m/board
usually 9
it could be overheating would have the samw symptoms
redo the paste on the cpu with some arctic silver
http://www.arcticsilver.com/arctic_s...structions.htm
Power Supply Information and Selection