Forgive me for the long answer, but I think its important that you understand the basics:
Did you change the product code between the 2 MSI versions? My guess is that you haven't changed the product code between the 2 versions and windows installer is considering
this as a minor upgrade. First understand the difference between Major vs Minor upgrade.
Minor Upgrade
A minor upgrade is an update that makes changes to many resources. None of the changes can require changing the ProductCode. An update requires a major upgrade to change the
ProductCode. A minor upgrade can be used to add new features and components but cannot reorganize the feature-component tree. Minor upgrades provide product differentiation
without actually defining a different product. A typical minor upgrade includes all fixes in previous small updates combined into a patch. A minor upgrade is also commonly
referred to as a service pack (SP) update.
Major Upgrade
A major upgrade is a comprehensive update of a product that needs a change of the ProductCode Property. A typical major upgrade removes a previous version of an application
and installs a new version. A major upgrade can reorganize the feature component tree. During a major upgrade using Windows Installer, the installer searches the user's
computer for applications that are related to the pending upgrade, and when it detects one, it retrieves the version of the installed application from the system registry.
The installer then uses information in the upgrade database to determine whether to upgrade the installed application.
Now during Minor upgrade windows installer uses the following rules to replace existing files - Because unnecessary file copying slows an installation, the Windows Installer determines whether the component's key file is already installed before attempting to
install the files of any component. If the installer finds a file with the same name as the component's key file installed in the target location, it compares the version, date,
and language of the two key files and uses file versioning rules to determine whether to install the component provided by the package. If the installer determines it needs to
replace the component base upon the key file, then it uses the file versioning rules on each installed file to determine whether to replace the file.
At the core of any installer is the actual installation of files. Determining whether to install a file is a complex process. At the highest level, this determination depends on
whether the component to which a file belongs is marked for installation. Once determined that a file should be copied, the process is complicated if another file with the same
name exists in the target folder. In such situations, making the determination requires a set of rules involving the following properties:
- Version
- Date
- Language
The installer only uses these rules when trying to install a file to a location that already contains a file with the same name. In this case, the Windows Installer uses
the following rules, all other things being equal, to determine whether to install.
Highest Version Wins—All other things being equal, the file with the highest version wins, even if the file on the computer has the highest version.
Versioned Files Win—A versioned file gets installed over a nonversioned file.
Favor Product Language—If the file being installed has a different language than the file on the computer, favor the file with the language that matches the product being
installed. Language-neutral files are treated as just another language so the product being installed is favored again.
Mismatched Multiple Languages—After factoring out any common languages between the file being installed and the file on the computer, any remaining languages are favored according
to what is needed by the product being installed.
Preserve Superset Languages—Preserve the file that supports multiple languages regardless of whether it is already on the computer or is being installed.
Nonversioned Files are User Data—If the Modified date is later than the Create date for the file on the computer, do not install the file because user customizations would be
deleted. If the Modified and Create dates are the same, install the file. If the Create date is later than the Modified date, the file is considered unmodified, install the file.
During a Minor Upgrade, the default file versioning rules can be overridden or modified by using the REINSTALLMODE property. The installer uses the file versioning rules specified by the
REINSTALLMODE property when installing, reinstalling, or repairing a file. The default value of the REINSTALLMODE property is "omus".
Now you have to decide whether you are going to do a MinorUpgrade or a Major Upgrade for your MSI. If it is a Major Upgrade, then by default the old version of the product is uninstalled
before installing the new version. Use the link "WIX MAJOR UPGRADE" below for more details on how to implement this. You can also set the below property
within the MajorUpgrade Element - to make sure that you can install an old version on top of the new version.
AllowDowngrades YesNoType When set to no (the default), products with lower version numbers are blocked from installing when a product with a higher version is installed;
the DowngradeErrorMessage attribute must also be specified. When set to yes, any version can be installed over any other version.
If you are sticking to a minor upgrade then, you will need to override the default file versioning rules using the REINSTALLMODE property as mentioned above and use the code "d"
d Reinstall if the file is missing or a different version is present.
Then use the following msiexec command:
msiexec.exe /i installer.msi REINSTALL=ALL REINSTALLMODE=vdmus
- MINOR UPGRADE
- MAJOR UPGRADE
- MINOR UPGRADE - Replace Existing Rules
- MINOR UPGRADE - File Versioning Rules
- REINSTALLMODE
- WIX MAJOR UPGRADE
Hope that helps!