Did you really have to enter a password or just confirm UAC?
Entering password means that you might be a Standard User, which in turn means that APPDATA must be fixed for you as Std User and for Admin under which installation is actually running.
Just a thought...
Ran it, entered Admin password at UAC prompt. Again some time while it starts to install. Then same Error 1606 message.
Logged off, signed in as Administrator and tried again. Same error message.
You may want to try the following.
Use the Windows Installer Cleanup Utility to remove all traces of Reader from your system. This is no longer supported by Microsoft because it can produce problems with Win 7, but you can still download it from from places like
Then, download the Reader installer from
and perform a clean install.
Thanks for the suggestion Claudio. Guess what? When I tried to run the Installer Cleanup Utility, I got the same Error 1606 message regarding APPDATA. I wouldn't have posted here as this is a Windows problem, but I can't find anything on the Microsoft site that I haven't tried and I know this forum has seen everything!