For 400-500 dollars you can buy parts that will make that P4 system look like a pocket calculator. I went through the same folly a few years back, trying to upgrade a P4/775 system - all money was wasted, except the $100 Corsair case (still using it). Recent hardware is priced very reasonably for the performance you get. Bus, RAM, and CPU speeds have all increased by large factors, and competition among vendors is stiff. Even for machines that only do office duty, the difference is incredible. Do a little research and you'll see how easy it is now to build a fast, economical PC.