Hi Ron,
If you click on the Prefs button on the SampleTank control panel, then Browse, is C:/Program Files (x86)/IK Multimedia/SampleTank 2.5/Instruments/ selected?
Every time I've run into those "Instrument Not Found" error, I've always found that it was pointed to the wrong folder.
I'd try selecting each of these folders and see if one of them allows the "Select Hi-Q" command to work:
C:/Program Files (x86)/IK Multimedia/SampleTank 2.5/Instruments/
C:/Program Files (x86)/IK Multimedia/Instruments/
If that doesn't do the trick, feel free to give us a call on Monday, I'm sure we'll figure it out.

Thanks
Kent
PG Music