Get new drive, backup data, replace clinking drive. You can get a 2TB drive these days for under $100USD.
As for drive noises, some older MFM or IDE drives had a copper grounding strap that contacted a carbon electrode attached to the rotating disc hub in order to drain static charges that built up in the drive internals which could, if not drained off, damage the electronics of the unit. Sometimes these would make a squeaking or squealing sound. Clinking on the other hand means that something is physically lose, and if internal to the drive, can destroy it when it lets go altogether. That said, it may just be something loose externally to the drive, such as one of the mounting brackets. You should probably take the cover off the system and check that out before going to the extent of replacing the unit. After all, tightening a screw is way cheaper than buying a new drive... :-)