HELP! Nothing on the screen

[MacVista]

Whenever my friend tries to turn on his computer, all the fans start and hard drive start spinning, but nothing appears on his monitor. What's really weird is the computer starts up as soon as it is plugged in; the power buttom is never pressed.

I've tried:
multiple monitors
a different working power supply
a working X850XT PCI-E
a GF4 MX420 PCI graphics card
using only one stick of ram at a time in the first slot

All of that didn't change anything

I even switched the Pentium 4 630 with a Pentium D 820, and the only change is that the computer shuts itself off after about 30 seconds of being on. (Still nothing on screen)

What do you think I should do?

Comp Specs:
Intel Pentium 4 630
Asus P5LD2 (using a 20 to 24 pin power adaptor with it, would that cause all these problems?)
Corsair ValueRam 1gb 2x512 PC2-4200 in dual channel
Asus ATI Radeon X700 128mb PCI-E
WD 80gb SATA hd
NEC ND-3520A 16x dvd burner

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Previous history with the computer: When the computer was originally built, both motherboard and cpu temperature readings were wrong (unless they're over 90 degrees celcius right when the comp is turned on -- so I disabled the temperature sensors). Over the last few months, the computer has just been shutting itself off randomly. I tried stressing different parts of the computer using various programs, and whenever the processor was at 100% cpu usage for a like a minute, the computer would shut off.
Then it just wouldn't start up one day and I'm at the problem I described above.

 

[Bozo Galora]

At first glance - it seems like something to do with CPU - temp or power. Apparently it DID work at one time. So you have failing component somewhere. Shutting down means major HW prob.
If temp was correct - 90C at startup - the Intel CPU would throttle itself in steps.
Then you would get a slowish PC with high CPU usage all the time.
You may also have shutdown temp too low in bios.

you should reseat HSF - CPU - definitely check LGA for bent pins - isnt that the delicate one you have to be real careful with inserting and removing?

you could try underclocking CPU to lower load - just as a test

you also mention using 20-24pin adaptor, but did not say whether SECOND PSU tried had intrinsic 24 pin ATX. That would be your next shot.

FWIW: starting up by itself COULD mean either the on/restart button in case is 2 piece and inner part is stuck inwards. Perhaps spike starting PC with plug blew something - mobo or CPU.

or....
mobo header bank has misplaced molex connectors from case, or shorted

or.....
someone scratched traces on mobo

or......
AS5 got on tiny mobo IC legs

(Quote)
Do the two following steps to make troubleshooting possible. The restarts can literally be anything

1)There is an option in bios under power manageemnt. Wording will vary but basically it says something like "restrat after a power failure" Disable that. Now if it was the power crapping out the system will go down and stay down.

and from windows help:

The next will let you see the blue screen of death. Uncheck the Automatic restart options.
2). To specify what Windows does if the system stops unexpectedly:

You must be logged on as an administrator or a member of the Administrators group in order to complete this procedure. If your computer is connected to a network, network policy settings may also prevent you from completing this procedure.

Open System in Control Panel.
On the Advanced tab, under Startup and Recovery, click Settings.
Under System Failure, select the check boxes that correspond to the actions you want Windows to perform if a Stop error occurs:
Write an event to the system log specifies that event information will be recorded in the system log.
Send an administrative alert specifies that your system administrator will be notified.
Automatically reboot specifies that Windows will automatically restart your computer.
Under Write Debugging Information, choose the type of information you want Windows to record when the system stops unexpectedly:
Small Memory Dump records the smallest amount of information that will help identify the problem. This option requires a paging file of at least 2 MB on the boot volume of your computer and specifies that Windows will create a new file each time the system stops unexpectedly. A history of these files is stored in the directory listed under Small Dump Directory.
Kernel Memory Dump records only kernel memory, which speeds up the process of recording information in a log when the system stops unexpectedly. Depending on the amount of RAM in your computer, you must have 50 MB to 800 MB available for the paging file on the boot volume. The file is stored in the directory listed under Dump File.
Complete Memory Dump records the entire contents of system memory when the system stops unexpectedly. If you choose this option you must have a paging file on the boot volume large enough to hold all of the physical RAM plus one megabyte (MB). The file is stored in the directory listed under Dump File.
Notes

To open System, click Start, click Control Panel, and then double-click System.
You must have at least a 2-MB paging file on the computer's boot volume if you select Write an event to the system log or Send an administrative alert.
If you choose either Kernel Memory Dump or Complete Memory Dump and select the Overwrite any existing file check box, Windows always writes to the same file name. To save individual dump files, clear the Overwrite any existing file check box and change the file name after each Stop error.

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http://support.microsoft.com/default.aspx?scid=kb;en-us;308427&sd=tech

 

[MacVista]

It worked perfectly for at least 3-5 months before the current problem of nothing appearing on the screen when the computer is powered on. There also wasn't any computer slowdown at all even with the high temperature readings. Unless the motherboard and cpu goes from room temperature to 85 degrees celcius in the time it takes for me to get into the bios and press hardware monitor, I doubt it's reading the temperatures correctly.

And, no the second power supply I used with it also does not have a 24 pin connector and was using the same adaptor. He also just tried switching the motherboard to another Asus P5LD2 and the same problem is happening. Right now, I'm starting to think that little ~$5 adaptor is causing all this grief. I guess I'll go buy another one and try it out. Does anyone have an opinion on what else it possibly could be?

Edit: Yes it is that delicate socket 775; pins on motherboard look fine. The Pentium 4 630 looks fine from a purely visual inspection. Nothing appears on screen at all right now, so getting into the bios to underclock or something is out of the question.