Remember a few months ago when we had a machine that so corrupted Norton Anti-Virus that it would no longer install, and we had to re-install the OS? Well, the same thing happened again - Error 1606 when trying to install NAV Corporate on a W2K box. The symptom was that the user noticed an exclamation point on the taskbar icon for it, and on inspection neither the engine or the on-access scanner were loaded. Not good. Uninstalled, then tried to reinstall. It failed with the aforementioned error 1606.
After a LOT of research, part of which led me into the registry looking at the User Shell Folders and Shell Folders configuration (not the problem), I found a link on the Symantec site which led me to a link on the MS site. Now, I had searched on MS and not found this same page that Symantec led me to. Wierd. It said that many programs, such as NAV installer, required the Windows Installer, which required the Windows Update mechanisms to be in good order. As a test, I went to the Windows Update site and it generated an error. Ah HAH. Tracking down this error led me to believe that I had several corrupted DLLs in the, buried in the depths of Windows.
The solution? Uninstall and Reinstall MSIE 6.0a - then re-apply the critical patches and such from the Windows Update site. I kept updating and rebooting until the update site said there were no more patches. Then I installed NAV Corp again, and THIS time it had no problems.