When ACT is installed, the demo file is located in the public folder
>> Users >> Public >> Documents >> ACT >> ACT Data >> Databases
However, when ACT is uninstalled the public location is not deleted and the PAD file remains unchanged.
If the computer name was changed between uninstalling and reinstalling, the PAD file in the standard location points to the PAD in the public location which then points to a computer name that doesn't exist.
When ACT is uninstalled, delete the Demo PAD in the public location.