I know the thread is old but anyway; if the 'tak' sound comes in intervals of fours (tak-tak-tak-tak|pause|tak-tak-tak-tak|pause, etc) then youve got a bad sector on your drive. I have an old Excelstor 80GB with two bad sectors myself, thats why i know this symptom so well. The good news is that on XP this isnt much of a problem because XP tries a couple of times then adds the bad sector to the internal 'sh'tlist'. (Meaning it wont try to use it anymore, which BTW goes for Linux systems as well.) The bad news is that on Vista and 7 youre totally out of luck because for some extremely stupid reason these systems keep trying and trying and trying and trying not realizing that it is high time to stop and just put that sector into the blacklist where it belongs. In that case all you can do is not use that drive at all because sooner or later the system will hit the bad sector and then it goes into a neverending loop of taks, blocking the entire OS, requiring a reboot to make it stop...