Windows XP

When you go and do the install and put in your product code it will return a message that directs you to call Microsoft. You will have to call them and just explain your situation. MS will wither provide you with registration information : ) or tellyou that you need to purchase a new license : (. I believe that you need an active internet connection at the time you call in because the license activation for your XP is tied to your machine's Mac Address (in order to make sure that people don't install the OS on multiple machines). Its also good practice to wait as long as possible (28th or 29th day) until activating the OS in order to ensure stability and avoid any of these issues if you need to reinstall. Good Luck and pls post the results.