I'm building an InstallShield project, which does a [Major Upgrade][1] to an existing install (i.e. I changed the `Product Code` while retaining the `Upgrade Code`).

The uninstaller of the previous version (which is already deployed) is broken, and fails to run some scripts. This in itself is not a serious problem, as all relevant files are removed beforehand.

The problem is that when the new installer attempts to uninstall the previous version, it aborts when the uninstaller fails. I've tried setting the 'Continue On Failure' flag (Media-->Upgrades-->MajorUpgrade-->Advanced-->Additional Settings), but with no effect.

Questions:

* Is there a way to configure IS to silently remove the previous version?
* If not, can I write some custom VB-action to silently uninstall the previous version?

**EDIT**

Not sure this is relevant, but here is what is wrong with the previous uninstaller:

The Installation sequence includes some custom actions. Two of these call executables which in turn install some device drivers. Obviously, they should only run when an installation is underway. Unfortunately, the previous designer did not set the 'NOT REMOVE' condition, which causes the actions to run during an uninstall operation. Thus the uninstaller fails (as it cannot find the driver executables).