Monitor goes to sleep when XP starts to load

This is a fairly lengthy post, but I want to explain the problem, and what I’ve done thus far to troubleshoot it.
First, the config:  XP Home sp2, component built PC about 3 years old, 2.4ghz Intel processor, old, but pretty reliable ECS mb, a couple ATA Maxtor HDs, 1 gb RAM.

The problem:  I saw a similar question to my issue, but the thread was abandoned.  Here is the link:

About 3 weeks ago, after some period of idle time, (from 2 minutes to 10 hours), the monitor would shut down, similar to sleep mode, but the LED would rotate every second from green to amber to green to amber, etc.

To fix it, I would have to do a brute force power down, unplug/plug the power supply and monitor, and restart.  The computer would work again.  

Then, the video problem started happening while someone was using it.  Within a day, the video problem (turning off, amber, green, etc.) would happen after POST, and XP started to load.  Other times, the video problem would occur immediately, and POST was not visible (or POST did not occur – I couldn’t tell, other than the keyboard light coming on for a couple seconds.)

Here is what I've done to troubleshoot.  
All cards and memory removed (and things dusted – I know, I’m just anal that way).  Cleaned and reseated CPU fan with new “heat cream” (I can’t remember the official name.)

With only the video card, RAM, keyboard connected, reset and reconfigure of CMOS, I started, was able to successfully make it through POST (including the simple POST ram test).  Of course, I still had the same video problem after POST and XP started to load.

Next step was memtest86 v3.3.  A few hours later, no memory problems found.  At this point, I presumed that the mb was probably ok (although not guaranteed), and the RAM was probably ok too.  Of course, the video problem remained.  (if only diagnostics would always fix the problem.)

I should mention that throughout this process, I sometimes had to reset CMOS to get the video to work through POST.  

I had an extra Maxtor 40g ATA hd and I decided to repartition, format, and a fresh install of XP.  Repartition, format and the first phase of XP setup worked great.  The next phase where it restarts and is supposed to boot on the HD, the video problem reoccurred.  I tried this same process with two other HDs, but the same result.

Next I swapped the monitor (I was reaching.)  No improvement.  I swapped the video card with a known working one.  The problem remained.

Next I swapped power supplies (three different ones.)  I swapped all IDE cables just for the fun of it.

After all of this, the problem remains.  The monitor goes to sleep.  This means that there is no video signal from the PC and if you power off and power on the monitor, you essentially have a monitor that has no video.

I have attempted to start into safe mode:  with and without networking, command line, etc.  It loads to MUP.sys and then it is gone.  The moment it should move into a graphic screen (such as the Windows XP startup screen) the video goes away.  

I am lost.  The problem is, I don’t know what to replace to fix the problem.  

Anyone have any ideas?
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Do you have  PCI video card you can test with? Maybe the voltage regulation on the AGP slot is gone.

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Well from your post its definetly a hardware issue because of the irregularity of the occuarance if it was software it would happen at the same point everytime.  I would say as ath has stated that the agp slot is going out or your motherboard all together must be replaced.

did you try to:

use your monitor, video card, and memory in another (working) pc?

(not all at the same time!)
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I would try using a different video card first. If you can borrow an AGP card, try that first. If that doesn't work, as suggested above, try a PCI video card (or if your motherboard has integrated video, try using that)

I would also recommend trying that monitor on another PC somewhere to make sure the monitor isn't actually dying on you.
pbbiiiAuthor Commented:
so from my initial post... i used another agp video card from the pc i'm currently typing from, and another monitor.  
i don't have a pci video card, so i won't try that one.  
i did use the ram in another pc, but didn't put the video card in another pc.  

At this point, i'm not sure i have the stamina to work on this one any more.  i was hoping, not expecting, that someone had actually experienced this phenomena before.

i'm going to assume the mb is going bad.  it's time to get another computer.  

try testing your devices with burnin test, or tufftest lite :                        Burnin test                              TuffTest lite

alternatively, you can run dxdiag from the run box to test video
Make sure its not Overclocked, Check the BIOS to make sure AGP is the selected Videocard at start up.

If you are getting video to the BIOS setup screen its not the card or slot on the MB. You have a problem with the PS or the mochine is overclocked on the AGP bus. Try locking the Bus at 66mhz in the bios.
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