The clicking noise, I'm afraid, is a very typical symptom of a dead hard drive.
You will need to bring the camcorder to an Authorized service provider to have it repaired. (It's likely cheaper for SONY to just replace it, so that's likely what they'll recommend.)
If the camcorder is out of warrenty, then you'll need to choose a replacement.
(I would never advise anybody to get a Hard Drive based camcorder. They are very susceptible to altitude, humidity, and temperature changes. They are also very sensitive to vibration and jerky movement.)
Before you buy a new camcorder, check out my 3 part Camcorder Buying Guide on my movie blog (Postings starting in November). It outlines the pros and cons of all your options.