Humor me for a while. Get a friend to help, as two heads are better than one. Assume nothing. Check everything slowly, carefully. Power supply lights up by itselt, tests good at the store., and is a top model Motherboard is new and a known top qulaity board. CPU and cooler are new and known top quality. Got official sounds when first attempted boot... then quit. We are not giving up on this computer, but we have to look at stoopied stuff. Something simple has gone wrong, or has been damaged, and it is so difficult to look for these things because it makes you feel stoopid to even look for these things. You could be looking directly at a problem, and your mind refuses to see it. You do have your memory properly installed? Remove extra modules so there is only one installed, and test, then replace with the other and test. We are looking for defective memory. Look very carefully at the socket for dirt, crud, bent or torn connect. Use a strong white LED flashlight if you can find one. Any change when you move this memory around. Remove the motherboard, do the sniff test for any smell of burnt medal or other burned materiasl. Examine the motherboard very carefully for any screw or hardware beneath the board that is grounding out the board. Is your board elevated from the case by at least a quarter of an inch on standard extensions? Are all screws protected by non-electrical connectors? Do you see any sign of damage in a bright light. Any possibility of a crack or rainbow colored metals. Any chance that they sent you a board that had previously been out of the box, and then resold to you as assumed good? Remove the power supply and look for any grounding... screws, wire, etc. Examine the case switch and the wires that go from the case power switch to the connectors to the motherboard. Can any of them be possibly in the wrong position or reversed. Sometimes the manuals have things exactly opposite. Do you have a volt ohm meter which you can use to test continuity? Do you have the little barrel-shaped capacitors on this board? Are any bent over? Us the light to examine for damage. Look for jumpers that have the clip off. Remove ALL other devices... hard drives, optical drives, and wrap their cables in plastic foam and rubber bands to be sure they are not connecting someplace. Examine all power cords, sockets. I once spent three days looking for a problem that was a defective power cord that cost 93 cents. Somewhere in there is a perfectly good computer with one 20 cent component causing a failure so obvious you cannot see it. Get back to us when you find it so we can all celebrate.