I did a clean install of Windows XP and now it is running painfully slow. Does anyone know why it would run so slowly and could it be a hardware issue that would make it run so slowly? It is an old computer but I need to run XP for my work Cad program. The program won't run on Windows 7 but I was wondering if it might run on Vista. I can't even run Windows update. Do you thing the difference between XP and Vista is so much that my CAD system wouldn't run on it?