Computer won't start, MB light is on

Here is my computer:
core i7 920
6 GB corsair DDR3 RAM
GTX 260
Asus P6T Deluxe V2

I came home today and my computer was off when I had left it running. The On/Off switch and RESET button are lit on the MB. I tried unplugging the PSU and switching it off and reconnecting in several working outlets with the same result. The first couple times I tried turning it on I heard a faint fan turn on but I am not sure which one. I am assuming the PSU or CPU fan? I do not hear the sound anymore.

What should my first step be in diagnosing the problem? I have my parents working computer which is some HP pre built computer. Would it be easier to test my PSU with a multimeter or to disconnect my parents PSU(assuming it is even compatible with my computer) and connecting it to my computer?
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  1. OK I am going to try that clip test. I just wanted to update and say that now when I start the computer the PSU makes a buzzing sound which makes it seem almost 100% a PSU issue? Am I correct in thinking this?

    I think Cooler Master has a 5 year warranty on the UCP-900s or at least I read that in the newegg comments I am going to check up on that tomorrow.
  2. Simpler to test your CPU with a multimeter.

    But first the paperclip test. If the PSU fan does not spin up, the PSU is almost certainly dead. Howver, a spinning PSU fan does not necessarily indicate that the PSU is good.

    Use a DMM to measure the voltages. You can work from the back of the main power connector. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire (standby power supply): 5 volts always on. The green wire should also have 5 volts on it. It should go to 0 volts when you press the case power button, then back to 5 volts when you release the case power switch. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

    The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.
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