I have a desktop that has been updated to Windows Xp. The desktop will not start up when I turn it on, and my installation CD has been lost. However I do still have the box that I purchased it in with the product key information on it. I am assuming that If I do not have the CD my system will not start. One of the messages that come up on it when trying is that the information has been damaged or corrupted and for me to insert this CD that I no longer have. Please Help