New System WOn't boot or Post

[TexasOne]

Im just going to start this off by saying I have not built a computer in about 3yrs so my knowledge is alittle outdated but here goes.

I just built this computer and I cannot seem to get it to post or do anything, I have reset the cmos/bios. I have checked the start switch to make shure it isn't it.
I have also tried using the power switch on the motherboard but it won't work. Whenever I plug in the PSU I can see a orange LED on the motherboard light up but the motherboard won't attempt to boot I also tried to reinstall the processor but it didn't do anything.
Please help! I don't know what to do next besides replacing the motherboard.

Parts list
PC power and cooling 750watt PSU
AMD Phenom 9850 2.5ghz quad core
2x2gb OCZ PC8500
640GB WD harddrive
BFG 9800GTX graphics
MSI K9A2 Platinum AM2+/AM2 AMD 790FX ATX AMD Motherboard
Antec Full ATX case
Windows Vista 64bit edition ultimate

 

[kamel5547]

Possibly the PSU, do the fans spin up or anything (on the PSU, case, etc)?

 

[TexasOne]

Nope the fans don't spin.

 

[TexasOne]

I pulled the power supply out of one of my other computers and installed it, the computer booted right up.
So i'm gonna go ahead and swap out the powersupply with one that works.