If you want to be able to reinstall XP on the same computer, in case of
virus or disk failure, then you want software that can make a disk (or
partition) image. Several programs are listed at this link; some are free:
http://www.majorgeeks.com/downloads3.html
But, be careful, some backup/restore programs work only if Windows is
working. Avoid those. Get something that can boot itself from CD without
Windows. I have used Acronis True Image reliably for years. Note that
newers versions of Norton GHOST can also do this; older versions used a
bootable floppy.
If you want to be able to boot the boot to fix somehting that is preventing
XP from working normally, then options include:
(1) XP recovery console, run from the XP CD (or from a floppy set available
free form Microsoft).
(2) Windows PE CD based on XP, if you can find one. This was restricted to
IT professionals, but copies can sometimes be found.
(3) Make a Bart's PE CD, using your XP CD and a small program available at:
http://www.nu2.nu/pebuilder/
(4) Try to make a Vista PE CD. I have heard that Microsoft id offering the
ability to do this to everyone, not just IT pros.
(5) Use one of many a free "live" LINUX CD images. These run form the CD,
and do not install on your hard drive. KNOPPIX is one of the easiest to
use, although a large download; KNOPPIX supports NTFS:
http://www.knopper.net/knoppix/index-en.html Other "live" LINUX CDs are
available at:
http://www.frozentech.com/content/livecd.php