If the application has Mutex, uncomment the line below, comment the InitializeSetup function out, and use the AppMutex. Here's a link to the a KB article that mentions several methods:Īlternatively, you might try this (UNTESTED) code in the InitializeSetup:

You might be able to find the Mutex (if it's got one) by using SysInternals Process Explorer and selecting the program / process and looking at the Handles (CTRL-H) in the Lower Pane. If the application has a Mutex, you can add an AppMutex value in your Inno Setup installer and it will display a message telling the user to stop the program.