Mobo lights up, system won't boot

[kj1212]

This is my first system build, so please excuse me if I'm missing something horribly obvious. I had the system up and running for about three weeks, and one day it just wouldn't boot up. The fans are running, the green light on the mobo is lit, the case lights were working, but the system wouldn't boot. Thought I had it narrowed down to the processor. RMA'd it, and bought another mobo (going to TRY to build another one), along with another stick of memory. So when I got everything back yesterday, I tried again. SAME PROBLEM!! I tried booting with just CPU and memory on, still nothing. Tried the old mobo, nothing. Tried a different PSU, nothing. Tried each stick of memory without the other, nothing. Checked every connection and jumper setting, nothing. Tried a different video card, nothing. Stomped around the basement in frustration, nothing. It looks like it turns on in sleep mode, as the hard drive led shows red. The DVD-ROM and RW drives won't open, either. The only idea I have is that my case doesn't have an SMI lead to hook to the motherboard, that I can tell, but it worked before without on the other mobo until that mysterious day that it wouldn't boot. What in the world am I missing? I've come to the point that I will build a statue of the person that figures this out, and place it in my front yard for the world to see. I'm that desperate. Thanks in advance for any help that anyone can give.


Here's my system specs

Asus P4C800 Deluxe
2 sticks Corsair XMS 512mb
Asus GeForce4 Ti4200 128mb vid card
SB PCI 512 sound
P4 2.4 Ghz processor
Allied 450W PSU

[Detritus]

Do you perhaps have a standoff/screw that is shorting things out?

[originel]

Are you getting any beeps from your motherboard? or is there an error code display?

i know this sounds silly, but have you tried plugging into another circuit (not just another outlet, but one on the other side of the house)? it's possible there is some bad wiring.

It sounds to me like it isn't getting enough power...for whatever reason.

Also you can get what's called a post card and it fits in a PCI slot which will do a diagnostic for you (if you got the money that is).

EDIT: oh hadn't thought of that. definitely check all of your screws connecting your mobo to the case.

[kj1212]

Wow, thanks for responding so quickly! I've unscrewed and reseated the board several times, so I don't think that's it. There are no beeps, nor does the display on the monitor come up. The monitor, as well as the computer, is plugged in. (HA!) The lack of power is a good idea, but I vaccumed out of the same outlet while I was stomping around the basement.

[meese]

Thats a P4 motherboard correct? There is a seperate 4 wire (two yellow and two black) cable that needs to plug into the motherboard. You may not have that one plugged in.

It comes from the power supply.

[kj1212]

Are you talking about the power supply cable? Both the 20 pin and 4 pin are plugged in.

[meese]

Yes thats the one, the 4 pin. If its not plugged in you get the symptoms you described. But you do.

The next thing I would try is BIOS settings. If something is not set properly there, you can get this type of behavior.

[kj1212]

I can't even get the system to post, so I can't get into BIOS to change the settings.

[meese]

Are you sure you connected all the cables from the case correctly? Is there a reset cable? Maybe try disconnecting it, then try to boot.

[Chuckiechan]

Re check all of the plugs the come from your case to the board. The little black square ones may be your problem. Make sure they are seated correctly and not mixed up. Check your HDD data and power connections. See if you can get an error message by disconnecting your keyboard. Try disconnecting the floppy, too.

Have you tried a different HDD to see if it will post?

Have you tried using only one stick of ram in different slots?

Also, if you have a volt meter you can test the motherboard plug if you can find a chart with the voltages. Someone here has one or search on Google.