Requirements to create bootable pen drive of XP:
1. Windows XP SP2 ISO file
2. Pen drive with 2 GB
1. Insert ur USB flash/pen drive to your system and backup all the data from the USB as your USB drive will be formatted during the process.
2. Now download WinToFlash SW or Unetbin
3. Install the SW and when run there is option
4. Click Create button to begin the bootable USB process.
5.. Run the tool, and browse to Windows XP DVD files
Then follow as on-screen instructions !
CAUTION: Ur computer must capable to boot from Pen drive which sets from BIOS !
The best thing you have to do instead of making your entire system bootable, is just download a portable Windows XP Operating System which could run from your pen drive or portable hard disk drive. However, it is not advisable to use the Operating System this way because it might create damage to your pen drive.