Best Answer JimboH , 14 June 2016 - 19:14
Thank you for your response, it helped me find a solution.
I didn't want to add any installScript to the basic MSI project however, as I am hoping we can eventually migrate to WiX (and am assuming I couldn't use it then) also the previous install (the one that was an installScript MSI) has been long deployed.
Here is what I ended up doing:
I ended up with 2 CA's one for 32 bit and one for 64 bit.
The 64-bit: "[SystemFolder]cmd.exe" /C "echo y | reg delete HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall\InstallShield_[ISACTIONPROP1]"
As a commit execution CA with execute condition: VersionNT64 AND IS_MAJOR_UPGRADE
Where "ISACTIONPROP1" is defined in an upgrade path (as the "Detect Property") to hold the previous product code.
The CA's execute in the Install Exec (after "WriteRegistryValues" and Admin Exec sequence (after "ScheduleReboot").
The 32-bit CA is almost identical except the condition has "NOT VersionNT64" and the registry path is different (basically w/o the Wow6432 in the path to the key).