Desktop won't boot to bios

[Augoose]

All,
I consider myself fairly experienced when it comes to computers but this problem has me stumped. I've got a old HP Pavilion A1250n tower which I have running Win XP Pro to serve as a Security Camera server. Long story short, about two weeks ago I noticed it had shut down on its own and both the CPU heat sink fan and the rear cooling fan were running on high. I assumed my motherboard had failed so I ordered a new one. After replacing it, I got the same symptoms, so I then assumed that my CPU failed. I replaced that - same symptoms. Won't boot to bios, no post- just spinning fans.
I replaced/swapped ram - no change. I removed PCI components and really everything but the CPU, power supply and hard drive - same symptoms.
The power supply is putting out various voltages on various pins - I didn't pull the spec sheet to see if all voltages were within specs and instead assumed that if I'm getting various voltages (3, 11, 5, etc) that the power supply is likely good.

What am I missing?

 

[82rude]

Many moons ago i had the same issue,i believe a new hard drive fixed it.It was a long time ago for sure.I now exclusively use a dell laptop.

 

[Augoose]

Thanks 82rude. I've tried booting without the hard drives (one with OS and one without) and still can't get into the bios with either motherboard.

The software that I run requires Win XP Pro and and the use of a PCI card, so I'm stuck with trying to resuscitate this old tower and can't upgrade to a newer computer OS or a laptop.

I've built several computers over the past few years including the one I use daily and it is frustrating that I can't figure this problem out. I suppose the next step is to replace the PS but I'm reluctant to keep throwing parts at this thing.

 

[jbcurt00]

Can you get the necessary software to run on a Windows XP Pro emulator?

 

[fishrdan]

I'd suspect the power supply, has it been swapped yet, or tested with a power supply tester?

Remove everything from the MB except the processor, connect a monitor and see if the MB complains about missing memory

 

[bruceb58]

You are pressing the F2 key repeatedly while booting to get into the BIOS right?

You do not need a hard drive connected to boot into the BIOS.

 

[MTboatguy]

Have you checked the BIOS battery?

 

[bruceb58]

Have you checked the BIOS battery?

The battery on my motherboard is just for the clock. I wonder how many modern motherboards still use a battery for the BIOS?

 

[MTboatguy]

The battery on my motherboard is just for the clock. I wonder how many modern motherboards still use a battery for the BIOS?

I have 3 ASUS MB I just bought on Thursday, that have BIOS batteries, I am building some computers for some friends and actually was surprised that they still use the coin batteries for the BIOS!

 

[Augoose]

All,
thanks for all the replies and help. Just to recap, the symptoms were no video, no boot to bios, and fans were running on high. Turns out it was indeed the power supply after replacing both the motherboard and CPU to no avail. Initially I didn't suspect the PS as when they've gone bad on me before they were completely dead - nothing like this.
I tested some pins on the old power supply and because I received varying voltages, I disregarded the PS as a possibility but after running out of options replaced it with one from a big box store.

Thanks all!