How to Install windows XP in SONY VAIO Vista

Is it ok if your files get lost forever?  If it is then what you have to do is when it says if you want to partition a hard drive space, you delete the biggest parition (which wipes any and all vista and files of the computer.)  Then it will ask you which partition you want use.  Use the one you just deleted, whhich is the biggest one.  It will ask you to format it and stuff, just go with it.  Then you will have XP instead of Vista!  (Warning: I warned you above that this way will wipe of vista and any other files-documents-photos-everything off your comptuer)