Cannot open older files using Autodesk Simulation 2013

[PipePakPat]

Problem

When I try to open an existing file using Autodesk Simulation 2013, nothing happens.  The file could be opened in the 2012 software, but not in the 2013 software.

Solution

The Autodesk Simulation 2013 software will change the file format such that 2013 files may not be opened in 2012 or older software.  This is a move that will continue with Autodesk products.  When opening an older file for the first time using the 2013 software, a message will appear asking the following:
 
"This model was created in an older version of the software and will be updated.  Once updated, this model may not open in older versions of the software.  Do you want to continue?"
 
There is also a checkbox which reads: "Do not show this message again"
 
If one selects this checkbox and chooses "No", then the older models will not be opened and one won't see the message above displayed.  If one chooses "Yes" while this checkbox is selected, then older models will be converted to the newer database schema and will then be opened by the 2013 software. 

To restore the option to choose this option, access the "TOOLS" ribbon and select "Application Options".  From the "General" tab, activate the "Warn when updating file to newer version" option and choose "OK".