Ok, so I currently have an Alienware M15X with Windows Vista installed on it.  If i were to upgrade to windows 7, do all my files/folders on my Hard Drive get deleted in the process?

If so, is it reccomended to backup your files on a hard drive or on CD/DVD?

and one last question, when I bought my Alienware computer it came with a windows 7 upgrade ticket.  If i lose the ticket, is it possible for Dell to send me a new one or tell me what the number on it is?