Forget WinPE, use BartPE...
http://www.nu2.nu/pebuilder/
You would just create the BartPE DVD as you would for a Bart CD...
Just burn the resulting ISO to a DVD media.
Now for the option to install WinXP SP2.
You must "park" the sp2 files somewhere on your DVD media, you can add it to BartPE ISO by using the "add files/folder from custom directory" option in pebuilder
Now you must "edit" the nu2menu (plugin\nu2menu\nu2menu.xml)
Add an option to the "programs" submenu that will "launch" the installation of your sp2.
Now you can boot BartPE and when you use the media as "autorun" on some PC you can install sp2
To make it all perfect you could "glue" all this into a pebuilder plugin... But will also work without...
Regards,
Bart.