I get the error message quoted in the title when attempting to upgrade from Reader 9.0 to 9.1. After downloading nearly 60M, the modal dialog says
"The following applications are using files that need to be updated by this setup. Close these applications and click Retry to continue."
In the area where such applications are to be listed, _none_are_. It shows only:
"Applications that are using Adobe Reader or Adobe Acrobat"
I rebooted the machine (WinXP SP2) twice. Same result.
I've wasted an hour on this travesty. What is the solution?
Sorry to bump up an old thred.
I too ran into the same error. It was the vagueness of the error message which surprised me.
What I used Unlocker [http://ccollomb.free.fr/unlocker/] on the folder "C:\Program Files\Adobe\Reader 9.0", it showed some 6 to 7 files in use by the Windows Search Indexer.
I unlocked all the files and was able to update Adobe Reader.
I had the same problem with a laptop running Vista.
There was an older version of Adobe Reader (version 7) already installed which seemed to be the problem. I uninstalled it then restarted the Reader 9.3 installation and everything worked fine.
Hope this helps