Hi @ all
it seems that the Wipe Free Space option is the only nice way of decreasing, or setting to win-defaults, a manually increased MFT.
My problem was, that I had set the MFT of my partitions with Diskeeper to a fixed size, which would probably never be exceeded - and therefore never be fragmented. I'm running 3 parallel Windows (C,D,E) for different purposes and have chosen quite good MFT-values for C: and E: (around 60% used). But on D:, my 'Working-OS', I set it much to high, to 400.000.
Currently everything I need is already installed ... full Office + tools, full Adobe CS + tools, full Autodesk, media .... and the amount of file-entries in the MFT is only around 110.000.
The problem is not lost diskspace, but it always annoyed me that it took so long to defragment the drive only because of this large MFT. Neither Microsoft nor any Geek-site offered a way to change that (the Registry... "1-4 setting" does not work on a manually set size).
So finally I found an "error" thread here , that Wipe Free Space clears unused MFT. Exactly what I was looking for!
After cleaning it completely, I'm able to set it again manually to ~150.000.
"This is not a bug, this is a feature"
Thanks an Greetings, Chris