You have two problems:
1. XP is not booting
2. The hard drive may be dying.
Repairing/reinstalling XP is **NOT** the solution !
You need a new hard drive. If you do not feel comfortable replacing it, go
to any PC shop for help.
Note that a PC shop should also be able to transfer the contents of the
current hard drive (if readable) to (a) CDs or DVDs, (b) a USB hard drive,
(3) a partition on a new hard drive. Or, read below how to save files
yourself.
As for saving your personal files, assuming that the hard drive is still
somewhat working, boot the PC from a CD, instead of from the hard drive,
then copy files form the PC, such as to an external USB hard drive.
Bootable CDs to perform this sort of "rescue" are fairly common and mostly
free. See the following list for many possibilities:
http://www.frozentech.com/content/livecd.php
My favorite is KNOPPIX, which is LINUX operating system and several
applicaiton programs. It comes as a CD image and as a DVD image. The DVD
image contains more applications. Both are ISO-type file that must be
burned to CD/DVD with programs like Easy CD Creator or Nero, which support
"burn from image". The CD image is about 700 Meg; the DVD image is much
larger. By defualt KNOPPIX does NOT install on the hard drive. It can read
NTFS partitions, such as those commonly used by XP. It also reads FAT
partitions (useed by win95,98,ME), as well as LINUX-type partitions.
http://www.knopper.net/knoppix/index-en.html
Info, help files, how-tos, etc for KNOPPIX are at:
http://www.knoppix.net/wiki/Main_Page