G4 Titanium Powerbook Beeps and sounds like a clock!

I have had my G4 Titanium Mac Powerbook 15 inch for many years, and upgraded it accordingly.
Lately it has started making a noise as if searching for something and has an occasional beep incorporated in that ticking noise. Sometimes freezing after these episodes.
I cannot find anything relevant to this problem, it is not overheating as far as I can tell, but it seems to do this after it has been on for a while.
I ran my external original CD on it and it came up with no problems.
Has anyone any ideas.

Sure sounds like an ailing hard drive to me

Could it be the battery?..... I noticed it went from 100% on plug in to 0 in no time flat. If its the Hard Drive, I wonder if its worth replacing?