Sigh....Can't Start My Custom Built Computer

Greetings Everyone
Been lingering around this board for sometime, and decided to upgrade my computer, from a amd athlon 3000+ to the following, but after the upgrades I can't start my computer. I hit the power switch and nothing happens.

Specs:

MOBO
GIGABYTE GA-MA785GM-US2H Socket AM2+/ AMD 785G/ A&V&GbE/ MATX Motherboard
http://www.newegg.com/Product/Prod [...] 6813128394
(got mine from ewiz)

CPU
AMD Phenom II X3 2.8ghz
http://www.newegg.com/Product/Prod [...] 6819103649
(got mine from ewiz)

RAM
Corsair DDR2 1gb
http://www.newegg.com/Product/Prod [...] 6820145525
(got from frys)

GRAPHIC CARD
Evga 8600GT
http://www.newegg.com/Product/Prod [...] A%208600GT

PSU
Viotek 550w
http://3btech.net/newv2vi5520p.html

HARD DRIVE
40GB 7200rpm WD
(yeah I know its too small, Broke)

TOWER
Cooler Master ATCS
http://www.newegg.com/Product/Prod [...] 6811119187

Prior to these upgrades, I got a free pentium 4 510 from a friend, I bought a cheap $30.00 ECS mobo, and ran it with the psu, gpu, ram etc stated above, but the board was dead, although everything powered up. Then I got the new board and cpu this week, and after assembling the thing, I can't get this thing to start up. Its in the same case, using the same psu, gpu, ram, etc. Just different cpu and mobo, what could be wrong here? Did I damage the plugs or something here??? All the plugs are in the right spots.....

Sigh.... I'm having bad luck these two weeks, I just want my comp to work.......
Any advice would be greatly appreciated. Thanks for reading.

I looked through the list of problems and can't pinpoint it.
I hit the power switch, psu doesn't run, gpu doesn't run, no lights, no fans, nothing. Just dead. Should I take off the gpu and see if it would start on its own, since it has a integrated gpu.

on a side note don't know if this would jack up the psu, when I was pulling the 8 pin out of the dead board, one of the wires did come out of the socket. But I pushed it back in so don't know whats going on now.

Sounds like the wire you pulled loose, is still loose.

Ok I think I found the problem but I am not sure. I took everything apart, and than re-assembled the computer. And this time I plugged in only the 2x12 12v atx connector to the board and the switches. The computer now turns on, but no signal on the screen.

Than I continued with other power plugs on the board, the next one I plugged in was a 2x4 12v atx cable. But once I got that in, the computer doesn't start up. So I unplugged that and the computer starts up again. This board is slightly different from my old set up so I am at a lost. Do I need to plug that 2x4 12v atx cable in?? and what purpose does it serve???

I can start the computer up if I only have the 2x12 12v atx cable in , but it leads me to a blank screen, can't detect signal.

I plugged monitor cable to the integrated gpu and than tried the evga gpu and same thing.

I plugged in the mobo speaker and no beeping noise's either.

Thanks for the helpful information, greatly appreciate it.

Well, Raidmax looks better and Antec has higher efficiency... I guess it's up to your preference. They both receive some pretty good reviews, though.