Bert,
As Larry has said, so far it seems as all the sounds can be loaded manually. This suggests that ...
(a) either the BIAB Hi-Q instructions are not working properly
(b) the Sampletank default directory is not properly set
Just to make absolutely sure that it's not (b), could you please load in the Sampletank soft synth (you're probably quite and expert at this now!) and go to preferences.

Check the path for the root directory. From what you've said, it should be ...
c:\Program files(x86)\IK Multimedia\InstrumentsAfter pressing "Prefs" (#1), I'd use the "Browse" (#2) button to navigate to the above directory and then hit OK until you exit everything.
We need to make absolutely sure that the default directory is set properly.
Also, after setting the above, close everything and fully power down your computer (do not simply put it on standby). Now restart the computer and see if the problem still exists.
Regards,
Noel