USBMULTIBOOT is perfect, I think we can put XP source and all necessary files on USB-DISK in one package such as ISO or IMG file and use grub4dos to boot it and install to local hard disk. There two obvious advantages one is safety the other is we needn't to care USBDISK's file format for we can select file type in ISO/IMG package.
Also I think we can boot this ISO/IMG via grub4dos installed on hard disk or usb cdrom or other device.
Maybe one problem is when map ISO/IMG as hd0 or else, is it possilbe? how about the speed?
I will try later.
ANY SUGGESTION?
THANKS.