wink wink,
When you do the install of WinXP, if you install on top of itself and during the install options, you tell WinXP to
Leave the File System Intact you will not lose any of your data short of what as in your Windows Directory.
Take Care,
Richard
P.S. I usually point people to this Slipstream Walkthough:
Slipstreaming Windows XP Service Pack 2 and Create Bootable CD