Hey I have a custom built computer and one day I come home from out of town and it refused to power on. When I went to push the power button all of the fan lights/fans would power on for a split second and then turn right back off. I took everything apart and put it together and still have had not success with it. One thing I did notice though is the '5VSB_LED' light is on whenever the PS is plugged in and switched on. I'm pretty computer savvy but I've not had experience with ruling out what is wrong with specific components although I can put a computer together no problem.
I'm not exactly positive what sort of motherboard it is, it's a part off my old PC so I forget.
It's definitely an Intel though.
Intel Q6600 CPU
Ge-Force 9600 GT GPU
G-Skill DDR2 PC2-6400, 4 of 1GB sticks.
OCZ 700W PS
I can provide more information if anyone needs to ask.
I'm going to try and figure out the motherboard details so hopefully I can have that figured out soon.