Question Hewlett-Packard Pavilion 3260 Motherboard issues, what to do?

[Beamanator]

Hello everyone,
I need help with diagnosing why my Hewlett-Packard Pavilion 3260 Will not display video.
Here is everything i have done so far.
I have checked the Pentium MMX processor,
I have checked the RAM, Cmos battery is good aswell, The power supply is good im assuming.
I put a POST card in and its not displaying any Code, just ---- dashes. The power supply is 80 watt AT ( the old style) with a 3 pin Processor power plug?? This is a very old computer i can barely find anything online about it, I contacted HP support and they sent me to 6 different people.
I basically want to know , how i can diagnose the problem. Where do i start. If a motherboard does not post, What comes before that? For example Once the power is plugged into the system, does it go to the CPU first? then where? How can i test to see what part is failing, I have a multimeter and i dont know what to do with it. Any help is appreciated , I just want to know what i can do to try and troubleshoot this. Please help.

 

[Lafong]

Is the personal data on this PC backed up anywhere?

Not sure if you could find a replacement motherboard if it came to that. It's around 15 years old.

How much money would you be willing to spend on this PC to fix it, rather than getting something else?

$100?

$300

More?

 

[USAFRet]

Disregarding the actual PC, is there any critical data on the drive(s) involved?

 

[Beamanator]

No, No, Its not about Data, or the computer. I have over 30+ computers. Its not about getting another computer, I actually got this computer along with a whole bunch. I just like it for some reason and would love to be able to fix it somehow, thats why im asking these questions. I want to know how i can troubleshoot and find the problem.