well, that noise will occur when your drive is switches between platters, I.E. a 60 GB drive, may be made out of 4 platters stacked on top of each other each 15GB. its possible that your drive is just switching between platters, depending on how frequently it occurs.
Most drive manufactures give you a tool to check the status of your drive, the IBM drive fitness test is one such tool, for ibm of course.
I've owned a quantum brand drive that clicked like that a ton, and it was fine, then again, I had a compaq at work start doing that and 2 weeks later the hard drive was dead.
Backup now just in case, run the tests, see what happens. Also, there are a lot of hard drive tools for windows that can analyze SMART data, IBM also has a nice one of those, which i beleive works on any hard drive, that will report any errors, potential failures, etc....