Core 2 Duo PSU problem?

So I'm building a system.

I've got 512 DDR2 667 G.Skill RAM, a Geforce 7300LE PCI-E card, and a core 2 duo processor in my machine. I get it all together, turn it on and get no video signal and no beeps. I discover I need a molex to eps12v 8 pin adapter. I get it. Plug it in. Nothing. Same problem.

What's gone wrong here? My PSU is crappy I'm sure. It was free with the case. 500w. Is it indeed the PSU or what? I can't test the components since this is my only system.

All it says is:
SWITCHING POWER SUPPLY
MODEL: ATX -500W P4

AC INPUT:

220v-50hz
110v-60hz

DC OUTPUT: MAX

+5v -5v +12v -12v +3.3V +5VSB
38a 0.5a 18a 0.5a 23a 2.0a

no indication of what manufacturer makes it. And on the back on the little red slidey switch I can read 110v.

Did you plug the 4 pin into the 8 pin receptacle yet? I've seen where some motherboards will work with the 4 pin in an 8 pin board. Beyond that, get a decent EPS power supply. You didn't specify which mobo you've got, but if it's looking for an 8 pin supply, it has to be up there in its demand. Do you have the connectors for all the buttons hooked up right? Is the power supply switch on?

Are you sure it doesn't have a black switch somewhere on the back? If it doesn't that is an odd PSU. I would double check the mobo connections for the power switch just to make sure. It would probably be just about as cheap and easier just to replace the PSU. Usually the one that comes with a case are total P.O.S. anyway so even a really cheap one would probably be better. I know that's not what you probably what to do but unless you bought the case locally it will cost you more to ship it back and ship a new to you then it would just to buy a new better PSU and be done with it.

Yes that would be a serious upgrade from what is in there now. It has about 10amp higher on the +12v rail alone. Tagan makes excellent PSUs. You can't go wrong with Tagan, PC Power, SeaSonic, Silverstone, are my favorites.

If there is no brand name on the PSU, you certainly need a better one.

Make sure the power switch on the case works. Interchange the power switch with reset switch. Even in a cheap case, it is unlikely that both switches are bad.

I think all of the late model Asus motherboards have a green LED on the motherboard that should be glowing with rocker switch on the back of the PSU is on, before the PC is powered up by the front panel switch.

The bare minimum you need is the motherboard, processor, power supply, and a way to the power supply on. If those three things are working, you should get BIOS beeps - probably indicating video or memory failure. That is an indication the the processor and at least part of the motherboard is working.

Several years ago, I salvaged case wiring out of a junk ATX case. I put the two switches, the red and green LED's, and a small speaker in a small plastic box. Plug all of these wires into the motherboard case connections. I can plug the PSU cabling into the motherboard and drives. Plug a set of KVM switch cables into the keyboard, video, and mouse connections and I can test without installing everything in a case. The KVM switch lets me test quickly without disconnecting working systems.

I have a 4 port KVM switch. I usually keep one set of cables free. It makes me pretty popular over here when friends have computer problems.

It definitely won't hurt and will at least eliminate that as a problem now and in the future. Often times low quality PSUs are responsible for a lot of system instability that plague a computer over it's lifetime. Games crashing because they are taxing the system too much and the PSU can't deliver enough juice, stuff like that people never realize can be attributed to poor power. The PSU you have now at the very best will barely run what you have. The PSU you are looking at has some head room so if you decide to buy another video card you have a little room to play with.

UPDATE 2:

It's the motherboard.