Drivelight flickering all the time

Hi all,

Vista Home Premium, 4GB, C:\drive internal, I:\drive USB

The accesslight on my 320GB D: drive containing ONLY Userdata music, pictures, documents started
recently to permanently flicker in a steady rhythm, say 20Hz. The drive sits in a dockingstation, on
top of the MEDION computercase and connects through USB 2.0

C: Drive 320GB has all programs and programdata on it, so they are completely separated.

When accessed it will either light up stronger or gets dimmer, depending on the amount of data read, then settles to regular flickering.
It used to be completely ON, except when accessed or written to.

The computer works allright but loading pictures or other data from D:drive is sluggish. Performance
of the drive is clearly lower, it is busy. It will also needlessly wear out sooner.

On startup, its light is steady ON (as it used to), and starts to flicker following userlogon and desktop visible.
During restarting the system, it will not stop to flicker.

Did the obvious scans, AVG, Spyware, defrag, empty Recycle bin, clean Registry etc.

Light's still on and flickering, as if contstantly acessesed by 'something'.
There is no outgoing activity to the Internet as displayed by my NetMonitor.

I have stopped, reset and restarted Searchindexer, which finished its job. No effect.

In Vista's Reliability and Performance Tool section Disk I can see no other permanent activity going on for
D:drive (other than valid acesses) but sometimes
D:\$MFT NTFS50-MFT Master File Table and

The latter 2 files I cannot see in Explorer nor in TreeSize.
How to access those for inspection?

Any suggestions would be highly appreciated.