Flashing green light on ASUS P8B75-M/CSM (computer wont boot)

[Inexperienced]

I built my computer (First computer I ever built. I was, and sort of still am inexperienced with computers) 2 years ago and it has been running fine without any problems until a few days ago when it would no longer boot. With the Power Supply powered on, the green LED light on the motherboard would normally stay on and I would be able to power on the computer. Now it is flashing when the Power Supply is powered on, and the computer no longer boots.

I did the following test:
https://www.youtube.com/watch?v=5FWXgQSokF4
to determine whether or not the Power Supply was the problem, and it doesn't seem to be as both the Power Supply fan and the case fan worked fine when the Power Supply was powered on separately from the motherboard.

Specs:
Motherboard: ASUS P8B75-M/CSM
Power Supply: Antec Earthwatts 380W

Not sure if any other specs are necessary, but I'll happily include them should anyone ask.

 

[popatim]

That's not actually a completely valid test, You need to at least measure the grey PWR_OK line which tells the motherbd that the PSU has determined that its voltages have come up and stabilized. The motherbd will not attempt to turn on (thus boot the system) until the power_ok line comes up too.
While you are measuring that for around 5v you might as well measure the rest of the voltages too.

 

[Inexperienced]

That's not actually a completely valid test, You need to at least measure the grey PWR_OK line which tells the motherbd that the PSU has determined that its voltages have come up and stabilized. The motherbd will not attempt to turn on (thus boot the system) until the power_ok line comes up too.
While you are measuring that for around 5v you might as well measure the rest of the voltages too.

How would I do this?

 

[popatim]

Digital voltmeter (aka: DVM) is what I use. You can find cheap ones for around $5 like this: http://www.harborfreight.com/7-function-multimeter-98025.html

There are also power supply testers you can buy like this: http://www.newegg.com/Product/Product.aspx?Item=N82E16899261023

 

[Inexperienced]

Digital voltmeter (aka: DVM) is what I use. You can find cheap ones for around $5 like this: http://www.harborfreight.com/7-function-multimeter-98025.html

There are also power supply testers you can buy like this: http://www.newegg.com/Product/Product.aspx?Item=N82E16899261023

Instead of doing that, I'm planning on just buying a new PSU, and returning it if it doesn't work (which should mean the PSU isn't the problem). I figured it'd be more practical since I'll pretty much never have to use one of those Multimeters again, and if the PSU is indeed the problem, I'd have to buy a new PSU anyways.

How do I determine if the new PSU is compatible? These are my following specs:
Old PSU that recently died: ANTEC 380W EARTHWATTS GREEN SERIES
Motherboard: ASUS P8 B75-M/CSM
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)

 

[Inexperienced]

Instead of doing that, I'm planning on just buying a new PSU, and returning it if it doesn't work (which should mean the PSU isn't the problem). I figured it'd be more practical since I'll pretty much never have to use one of those Multimeters again, and if the PSU is indeed the problem, I'd have to buy a new PSU anyways.

Just bought an Antec 450Watt VP450, and still the problem persists. Guess that rules out the PSU being the problem. Any suggestions?
Also, the green light blinks roughly once every 2 seconds when the Antec 380W is connected, and roughly 5 times per second when the Antec 450W is connected.

 

[Inexperienced]

Bump

 

[Inexperienced]

Bump

 

[popatim]

ok, the only light that should be flashing on that motherbd is the Dram Led up by the MemOK button which is just above the big 24pin motherbd power connector.

Is that the one flashing? If it is Press and hold the memok button until it starts flashing and then wait until it either goes out (should boot up) or turns on steady (bad ram)

If it turns on steady - power the system off. If you have 2 sticks of ram they should be in A2 and B2. remove all but the A2 ram. power up and then press and hold the memok button until the Dram LED starts flashing. Give it a few minutes to see if it goes out and the system boots up.
Shutdown and remove the ram from A2 and stick in another. Retest in exactly the same way. Hopefully one of your ram sticks will let you boot up.

Your manual if you need it: http://dlcdnet.asus.com/pub/ASUS/mb/LGA1155/P8B75-M/E9142_P8B75-M.pdf

 

[Inexperienced]

ok, the only light that should be flashing on that motherbd is the Dram Led up by the MemOK button which is just above the big 24pin motherbd power connector.

Is that the one flashing? If it is Press and hold the memok button until it starts flashing and then wait until it either goes out (should boot up) or turns on steady (bad ram)

Hey thanks for replying.
No, that the Dram led isn't the flashing light; this is the flashing light in question:

 

[Inexperienced]

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[Inexperienced]

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[Inexperienced]

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[Inexperienced]

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[Inexperienced]

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