POST card codes might help, if you think the mobo is worth the expense. Obviously you need a card with PCI connector but it should be no problem getting one with both PCI and ISA. Just a warning though, always make sure you've installed it correctly in the slot. The orientation between ISA and PCI is different and it's easy to mix it up. I knew about it and still managed to get it wrong once, fortunately without any nasty consequences.

Just FYI, this is a VIA mobo but back in the Athlon XP days I had plenty of SiS motherboards that would just die on their own. Some were even broken (or semi-broken) out of the box. ECS was the worst offender. I guess everybody wanted to make them fast and the quality suffered, perhas the BGA soldering wasn't all that great. Or it could be the chips themselves that died, who knows. Point is: I've never dealt with as many bad mobos as during that era.

tick tock and SHHHRERGFHRHHR noises might be blown mosfet actually, or something shorted and protection kicking in.
do you have another motherboard to test your ram and cpu?

MOSFETs are good. NOT Blown

also this time i will replace the AGP and DIMM caps in some day

I tested the CPU on a healthy ECS K7VZA and it is good. So BOARD is problem. I will repair it someday.
Also tested memory on another board and it works.
So Motherboard is culprit

I also plan to get rid of all Choyo capacitors, even small ones. Reason for this: it fried a PS/2 keyboard, so I need to replace also the smaller caps. Just for my safety.