How to notify users when a major upgrade is being run
Windows Installer Major Upgrades silently uninstall the previous version(s) by default. This article describes how to notify customers when a major upgrade is being run and an older version is being removed. By default, a major upgrade looks identical to a first-time installation, displaying the default InstallWelcome dialog box.
To inform the user that a major upgrade is about to take place, you can add a text control to the InstallWelcome dialog box, and conditionally display the control only if the FindRelatedProducts action places any old product codes in the action property. Because the FindRelatedProducts action runs before InstallWelcome is displayed, you can safely use the action property from the Upgrade table in conditions.
The following steps create an installation that provides notification of a major upgrade:
Select the major upgrade item from the Upgrades view.
Click the Advanced tab and take note of the Detect Property listed in the Additional Settings section. This property is set if a previous version targeted by a major upgrade is found and remains null if no such version is found. By default, this property is called ISACTIONPROP1.
In the Dialogs view, modify the InstallWelcome dialog to add a new Text Area control that will display when your install is running as a major upgrade.
On the Behavior section of the dialog, select the control you have just added and add the following conditions (replace ISACTIONPROP1 with the property found in step 2):
Action: Hide; Condition: Not ISACTIONPROP1
Action: Show; Condition: ISACTIONPROP1
At run time, the text control will be displayed if the install is running as a major upgrade or otherwise it will be hidden if the install is running as a first time install.