Flashing green light, computer won't boot

[Inexperienced]

My computer stopped booting up after 2 years of running. With the Power Supply powered on, the green LED light on the motherboard would normally stay on and the computer would boot. Now it flashes when the Power Supply is powered on, and the computer no longer boots. This is the flashing green LED light in question:

These are the following specs:
Motherboard: ASUS P8B75-M/CSM
Power Supply: Antec Earthwatts 380W
RAM: G.SKILL RIPJAWS-X DDR3-1333 8GBXL (2 of these) & G.SKILL F3-10666CL9D-8 4GB (2 of these)
Videocard: EVGA GeForce GT 430 Part Number: 01G-P3-1431-KR
CPU: Intel Core i3-2120
Hardrive: Crucial M500 480GB SSD & Sandisk Extreme 120GB 2.5 SATA
Monitors: Dell U2412M 24" (2 of these)

I replaced the PSU with an Antec 450Watt VP450, and still the problem persists.

 

[alexoiu]

If starting the board with only CPU and CPU fan installed, does the CPU fan spin?

 

[Inexperienced]

If starting the board with only CPU and CPU fan installed, does the CPU fan spin?

I'm not sure what you mean by this. The motherboard can't start in the first place (nothing happens when I press the power button), so no fans spin.

 

[alexoiu]

By starting I mean pressing the power button.
There's a paper clip test for power supplies: https://www.youtube.com/watch?v=5FWXgQSokF4
See if a connected fan does spin.

 

[Inexperienced]

By starting I mean pressing the power button.
There's a paper clip test for power supplies: https://www.youtube.com/watch?v=5FWXgQSokF4
See if a connected fan does spin.

I tried that and both the Power Supply fan and the case fan worked fine when the Power Supply was powered on separately from the motherboard.
Also, I tried another PSU and it still didn't work.

 

[alexoiu]

Then it might be a motherboard issue. But, try removing all components, but CPU and CPU fan, If still the CPU fan does not spin, then board is probably defective.