Question : Problem: Why does one of my hard drives make a loud clicking sound every now and then?

Although my computer running XP pro appears to be ok, every so often one of my 3 hard disks makes a louder than usual clicking sound.

What should I do?

Answer : Problem: Why does one of my hard drives make a loud clicking sound every now and then?

Get the UBCD http://www.ultimatebootcd.com/

Download links are the icons at the top of the page above Overview.  Browse the page and see what utils are there for you.  Check the memory and hard disk utils especially.

Make the CD and boot from it.  

Then test the hard disk with the correct manufacturer's util for your hard disk.  Do the long test.  That will most likely diagnose any disk problem.

The sound may be normal.  It just may be a characteristic of that disk.

Also examine HDTune http://www.hdtune.com/ (the free version).  This can give an indication of the state of your drive.  Indication only.