For a processor, I'd go AMD Athlon.
I know very little. I currently have a 478 socket, 1.80 mhz p-4. I either need an onboard video card, or advice on what motherboard and card to get. I assume my DDR memory sticks will fit, and hoping my sound card will too. I just see no reason to buy an entire unit, when my tower and power unit is strong, dvd burner, cd player etc are still good.