HP Laptop randomly boots with hw change

I'm working on a customer laptop that is a HP dv6000 laptop with 160 gb hard disk, wireless internal network, 1gb memory and windows vista home premium.  

The customer reinstalled vista from the disks (I assume) and after the install was complete, the machine would come on like it was booting but nothing showed on the screen... the monitor will not even light up.  

After I got it, I played around with it and removed one 512mb memory stick and it posted that the memory size had changed, I think.  Either way it posted.  I reset the bios to default and tried to boot it again and it just boots.. nothing on the monitor, not even a light, and then after 15-20 seconds, all the lights on the dash go off and come back on, the dvd rom spins up like it is trying to boot from the disk but still nothing...  It just keeps looping.  

I removed the battery, the cmos battery, the memory and the hard disk and let it sit for a while and then put in a bootable cd rom, and with NO hard disk installed it booted to the bios and the cd rom so I tried to reboot it and still the same looping reboot with nothing on the monitor.

I thought it might be the hard disk (over the phone) and once I got it here, I couldn't pinpoint it since I can only get to post once every three days of trying.  I'm assuming there's something else wrong since I can intermittently get it to post.  Does anyone have any suggestions, or is there some FUNCTION keys that I can use to get this thing to come on at least a little more predictably?   I am reluctant to disassemble the machine if I don't know what the problem is for sure.  Maybe a video problem?  I'm completely lost on this one.

The customer gave a poor explanation over the phone which is why I assumed it was a failing hard disk, but it won't even post most of the time so I'm not so sure the hd is defective.  It powers on every time but if it doesn't post, it is an infinite loop of lights on.... 20 seconds.. flash off and back on for another 20 seconds.  Only when there's a hardware change will it think about posting and it won't post anymore after I change memory sizes.  I left the batteries out over the weekend and holiday, and it booted on the first try with no hard disk and booted right up to the FBI Tools CD Rom, but then nothing after a reboot again. and again.

Any information would be greatly appreciated.
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Very easy diagnosis. Faulty Mainboard.

More than likely the Northbridge controller has failed therefore could indicate a problem with either RAM, HDD or CPU. Replace the Mainboard which will solve your issue.

mikesgAuthor Commented:
I just got it to post again.  I have pictures of what the message is when it DOES post.  This time and I think thelast time it posted it was warning me that the system time had not been set.
I just took these pictures.  There is no hard disk in the machine, 1.5 gb of memory, and the cmos battery is still unplugged at the time of these images.  I took the first pictures, went into the bios and set the time and then took the last four.   The default date was 01-01-2006 and the time was like 00:01:43 or something like that... which is expected after unplugging the batteries.
Immediately after taking these shots, I changed the boot order and put the "floppy disk" way down at the bottom, since there is NO floppy disk drive in the machine.   Im wondering if a bios flash would be in order here....if I could even get it to boot again to do such a thing.  After changing the boot order, Save and Exit the bios, ....back to the loop rebooting with no hint of life on the monitor.  I have even taken a flashlight to the monitor to see if I could see anything as if maybe the backlight is failing but the monitor was completely OFF.
Any suggestions?  There were no posts when I started this reply so forgive me if I haven't seen a post yet.  I took the pics with my cell phone which is why there are so many, just in case they weren't clear.

mikesgAuthor Commented:
another diagnosis?
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Ok the problem looks like its a BIOS related issue. It is totally possible that if the BIOS EEPROM has failed that your system will intermittently not boot.

yet again it is still a mainboard issue unless you have the equipment to reprogram the EEPROM.
mikesgAuthor Commented:
Thanks for your prompt response.  In case you were wondering, I wasn't meaning to be smart by my last post...  I know how it looked after I posted. I meant is there anything from these images that lead you to believe otherwise?  
I'm going to give it a go and see if there is anything that HP can tell me...i.e. warranty info.. or recalls before I have the customer come out of pocket for a new mainboard.
Thanks again for your information and timeliness.
No problem at all...

This is what i believe you are looking at... Either a BIOS EEPROM issue or a Northbridge Chipset.
Either way its going to require a mainboard replacment...

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mikesgAuthor Commented:
For your reading pleasure... err... laughter.  LOL!  This is a known POS.
For the record, I work for Hartford Computer Group ...warranty work... and I own my own computer repair business and it is almost dreadful when I get a trouble ticket on a HP/compaq.  The motherboards have to be tattooed every time and the hard disks have to be done the same.  It's all a racket.  I would buy used junk before I would one of these machines.  All the ones I have now were given to me and I'm looking at just what I can see right now and I'm counting 23 machines in plain sight and every one is HP and one emachine and one compaq.  What a heap of junk.
mikesgAuthor Commented:
Thanks for the prompt replies.  Now I've got to start back answering questions so I can get some points.  I'm starting to get low.
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