Does the computer beep? Did you plug in the cpu fan? Did you use the stand-offs behind the motherboard? Do all the stand-off's line up with the holes in the motherboard? There are holes on the motherboard tray that are for use with different form factors, if you use the wrong ones the motherboard will short out.
Double check all your cables.
Did you use a guide to help you assemble the PC?
The animated guide to Building a PC. Learn to build a PC from scratch with PCitYourself!
After looking at your parts the power supply stands out as a very poor choice. A 1100w power supply made by a unreliable manufacturer is an unreliable power supply regardless of the wattage claims. You would of been better off buying a High-Quality 650 watt power supply.