My guess is that you have your Linux on one big partition (including your /home), you should then back-up your data to an external drive.
Next step i would do, is use the recovery tool in your XP install disk to put back the old window boot loader with the command (fixmbr).
Then install your new Linux (whatever version) in your old Linux partition, the installation will format, install the new OS and grub will see your WinXP and added it up automatically.
There is other method (all good) but this is the most simple, i think.
Last edited by Davno; 03-05-2010 at 10:26 PM.