If you are interested in doing routine disk maintainance,
Norton Utilities comes with a disk checker/fixer called
Disk Doctor. however, I do not think that the version for
XP is any better than CHKDSK, which comes free with XP.
In both cases you must request a repair in windows mode,
then reboot for the repair to happen. XP's CHKDSK can
also be run under the XP recovery console, which can be
run directly from the XP CDROM.
If you are looking to recover files from a disk with a bad
file system, bad boot record, etc, there are many programs
that can find and retrieve files. Do a web search
on "file recovery", "undelete", "unformat", "file
restore", etc.