AFAIK, those are not very advanced graphics adapters, so they will probably be kinda slow in Windows XP. I've heard rumors that WinXP uses some DirectX functions to accelerate it's 2D interface. If so, then that explains why it slows down almost 2X when you enable the "Luna" skinned interface functions. Thus, you might want to switch to the "classic" theme, and go to System properties > advanced > performance settings > adjust for best performance.