I installed Windows Vista Business tonight. It said that it was going to save all existing Windows version files into a folder called Windows.old. I was wondering if it would be ok to delete that folder? I plan on sometime before I go back to school putting XP professional back on it. I just wanted to know if I could delete it or will it be a bad idea if I did so? I just like to know what your outputs about deleting Windows.old folder is? I thought when I did an install of a operating system it would have got rid of the old files. It kept everything that i had on my old operating system. That is the main reason I did a reinstallation. Now I am worried about if I did a clean install and put vista on again, it will say the product key is unavailable. Is keeping the old files part of vista? I know with XP you can delete that partation to make it a clean install.