Computer wont boot after some parts replaced

[Lone Puma]

So during the past week or so i started to play more CPU and GPU demanding games and notice that my CPU fan started to get extremely loud during game play, so i read some stuff online and came to the conclusion that i should buy a new CPU fan since i still had the stock fan that the original CPU came with. I got the fan today and proceeded to watch a video on how to install, everything went fine i got the new fan installed just fine got my motherboard back in my case just fine and started to reconnect all the wires. Well i got all the wires connected and plugged it in and hit the power button on the front of my case and nothing happened. I mean nothing at all, it was like nothing was even in the case. When i first build my computer i forgot to plug 1 power cord in and it would turn but not everything would. I just find it very strange that nothing happens at all and i really need some help on what to do.

My Specs are:
CPU: AMD Phenom II X4
Motherboard: Gigabyte 990FXA-UD3
GPU: Gforce GTX 550 ti
Power-supply: 550 Watt cooler master
New CPU fan: Cooler Master Hyper 212 Evo
Old CPU fan: stock fan

Thanks to anyone who takes the time to try and help me out

 

[Ayman IBreak]

you must have replaced some wires with others
check your mobo manual it can help if it didn't
take your pc to someone who can help
if you can take some photos of wires i can help you better

 

[chrisso]

Yes, go over the wires again, making sure you connected the cpu power lead by the processor. Dont forget to put the 4 extra pins in the main board power socket, nothing will happen if it needs those.