The truth is, you don't need anything else and many if not most of the
so-called tools applications often cause more trouble than anything they do
to help. There are faster and fuller featured defragging applications than
the default XP application; I use PerfectDisk from Raxco, www.raxco.com but
for most other things it really isn't necessary.
Also, Chkdsk is pretty weak as a disk scanner but if you don't have the
tools disk that came with your hard drive, you can download it from your
disk manufacturer and it will do a pretty thorough diagnostic of your hard
drive and it's free.