> [..]
>ISE will not automatically overwrite your files. ISE has a Program Id and Upgrade Id. If you change the Upgrade Id, the user machine pops up a message saying go to the Control Panel and Remove the older version first. If you change both values, it installs okay (without any message prompt) but your app still users the old version and a new version appears in the Control Panel Add/Remove programs section.

See if the info in Document Q105223 of InstallShield's KB applies.