Why? Well let me tell you a little story first. I upgrade my personal PC quite often. Every few months I may add a little something like more memory, an upgraded video card, sound card, DVD writer. Every 12 to 18 months I'll replace something more significant like the CPU or motherboard. It's these last two items that are going to cause a problem. It's also these last two items that PC enthusiasts will change often enough that they will be required to purchase a brand new copy of Vista...