06-24-2009 05:29 AM
First make Vista backup. If You have it now. How to do it all informations here.
Then put Your XP CD and boot from it. Select this partition which You want for installation.
Remember then this partition which You will choose will be formated and You will loose all data from it.
If You will need any other answers then please write down Your p/n number which is under Your computer and looks like this.