I got some new parts the other day (eg7650 cpu, gigabyte ga p35 ds3l mobo, corsair 620hx psu) and today I WENT about removing my old mobo/psu/gpu etc. Installed everything, seemed to go smoothly, no issues getting anything in there and connected. Replaced the cover, got my monitor/mouse/keyboard plugged in, plug in the power supply, turn it on, and hit the power button.
Nothing.
Turn it off, unplug, open it back up, check the connections, everything looks fine so I try switching the power/hdd/power led wires to see if i had them the wrong direction, close it up and try it again and same thing.
As far as I can tell all my connections are good but I can't get it to start up, I don't get any response whatsoever, does anyone have any ideas?

Ok, a little confused. Your subject says no power, but you said you turned it on and then turned it off.

Did something turn on when you pushed the power button?

If the computer sounds like it's starting to turn on (the PSU fan activates, etc.) but you only get a black screen, you most likely need to reformat. When you change motherboards, you change chipsets. Most of the time these are not cross-compatible with other motherboards and a reformat of the HARD drive is required.Sorry for the confusion, no, it didn't turn on at all, I meant that I turned off the power switch on the psu to safely unplug it. I don't THINK the led on the board even lit up.
When I hit the power button the fan didn't even start to spin, there was literally no response at all from the computer.Ahhh ok... I see.

Double check all the power cables. Make sure they're all on and connected properly. Sounds to me like the PSU might be defective though.Okay, that's the same response I got from some other PEOPLE. First thing tomorrow I'll check all my wiring again and see what else I can find.make sure the connections going out from the power supply are secure. i have the exact same PSU and i dont know about you, but i kinda had to fight to get mine to clip in correctly.

PROTIP: make sure the recepticle that you are plugged into has power before assuming its the PSU. it may just be as simple as a blown breaker. OK well....

See when ever IVE changed a motherboard from computer to computer , Ive never ever ever ever , got power straight away . odd thing happened to me today , i plugged everything in , no power , then i hit the reset button and bingo power , you got to move wires about and all that , try booting with only 1 stick or memory , take out your gpu , make sure if you have any LED lights there all in the correct places on the motherboard ......

Tony