I salute you Sir, there are not many men with the strength of character to run Windows XP, on a machine older than their KVM switch. Your quest for a PCI 32-bit graphics card fast and good enough to handle PCB Software design and CAD, shall not go unanswered.
The Graphics card that you seek Sir, is the GeForce 6200 DDR2 256mb PCI.
Your quest may take you to the ends of earth and you may have to slay many monsters in order to even behold such a card and then to rescue it and bring it back to your home.
Alternatively, you can easily find one on ebay.
This is my personal card below; I have used it many times in the past.
I truly admire your bravery and hope you find what you quest for. I am presuming that the HP Pavilion a310N uses a different motherboard to the HP Pavilion a310. As with that machine, you could have used the free AGP slot. I have included a pdf of the HP Pavilion a310, if you could obtain an old motherboard from one of these, it would be a straight swap XP would recoginise it. And you could run a graphics card that was 4X faster using the AGP slot.
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