Hey everyone... i recently got an old E-Machine PC... Model H3512. first thing i noticed upon opening the case is that the motherboard has a 24pin ATX connection, but the PSU only has a 20pin, so the far right 4 pins do not have any of the cable plugged in.
i have since tried to upgrade the pc (cpu [p4 3.0ht], pci-e graphics and new ram) and it just doenst seem to be working right, stalling out alot, memory read errors etc...
i have exhausted all the troubleshooting steps, only thing i can think is it has to do with the atx motherboard power, 24pin vs 20pin...
It might not be the lack of 4 pins, it could also be that the power supply is rated too low for the new parts.
My P4 3.0 ran on a 20 pin PSU + 4 pin ATX12 for ages, no problems. It was AGP though, and graphics card might've been less power hungry than yours.
What is your PSU rating?
You can try the adaptor above, but I'd be swapping in a new power supply, nothing crazy or expensive, just something with the right plugs and enough juice. But a bad motherboard or bad RAM can cause instability and RAM read errors as well..... e.g. if you ran around in woolen socks playing 'catch the RAM' it could be the issue too lol
Best of luck, good thing about machines like those is you can usually get bits for testing cheap or mates with spares.
Any part you can swap for another one, try it basically.