Through trial and error I found that a registry cleaner bundled with my Sony Vaio VPCF120FD laptop was cleaning out / deleting files related to the uninstall files for PGP Desktop 10.x.
Workaround was to:
1. configure the Sony "Vaio Care" registry cleaner to NOT clean out uninstaller files,
2. uninstall PGP Desktop V10, and
3. reinstall PGP Desktop V10
While not a windows techhead, am guessing this might relate to accidental deletion of the PGP Desktop msi installer referred to in an earlier pos on this this problem.
PS For sony vaio laptop users, open VAIO Care, click on the settings icon near top right of screen, click on the "Registry Cleaner" in the left pane, and then deselect (i.e. remove tick from) the Uninstall option.
PPS For others running Windows and using various registry cleaners, you might want to see if there's a similar configuration option available that you could deselect.
Best of luck! It always helps.