First System build not working? Help please!

Hey, for some reason my PC doesn't seem to work on the first boot. When I flip the switch - Not press the power button on the front io- a bright light flickers very quickly in the machine, which I believe is the LED on the motherboard. This is my build: 

AMD Phenom II X4 965 Black 3.4GHz Quad-Core Processor
Asus M5A97 LE R2.0 AM3+ Motherboard
Seagate Barracuda 500GB HDD
4GB Corsair XMS3 Ram (1 stick)
Zotac Geforce 9600GT AMP! Edition
For the case and PSU : "K3 Gamers PC Tower Case" and "650W Power Supply Unit"
Link for that here

Any help here would be really appreciated, this is my first system build, after all, and I reasonably large step up from my previous PC which quite frankly sucked ass.

Follow this checklist to make sure everything is ok on the build side. (click the "see full content" link in first post)