Thanks very much, Erik. But, er .. Tracker Update (TrackerUpdate.exe) is PDF-XChange Viewer's component for updating from within the program. It doesn't produce executables, or so I would think. I do not understand why HMPA would lockdown TrackerUpdate.exe. Nor do I understand how PDF-XChange Viewer could be updated successfully, while I used the updater component for updating and the updater component was locked down. Perhaps it could be wise if SurfRight could have a look at HMPA's reaction to TrackerUpdate.exe. Just to be sure, I ran PDF-XChange Viewer's current installer, PDFXVwer.exe 2.5.316.0. That worked fine, without interruption.