I have found WinXp will run fine on a 500-800 Mghz system as long as it has over 256 megs of RAM. A friend from work brought in his Dell 1.8 Ghz system with 128 megs of RAM running XP because he said it was running so slow. I checked it out, put in 512 megs or RAM and he was set. He couldnt believe the performance increase.