While upgrading, installing or uninstalling a Windows software package (such as iTunes for Windows or QuickTime for Windows), you may receive the following error message:
Could not access network location %APPDATA%
This is a 1606 error message (even though installers for Apple-created Windows software packages typically do not return the 1606 error message number with the message).
So, first try the automated Fixit from the following document:
If the problem persists, next try the automated Fixit from the following document (which should be effective against a different class of causes for 1606 errors):