The MSI package is designed to uninstall previous versions of OpenAFS for Windows during installation. Note that it doesn't directly upgrade an existing installation. This is intentional and ensures that development releases which do not have strictly increasing version numbers are properly upgraded.
Versions of OpenAFS that are upgraded by the MSI package are:
OpenAFS MSI package
Upgrade code {6823EEDD-84FC-4204-ABB3-A80D25779833}
Up to current release
MIT's Transarc AFS MSI package
Upgrade code {5332B94F-DE38-4927-9EAB-51F4A64193A7}
Up to version 3.6.2
OpenAFS NSIS package
All versions
Note that versions of the OpenAFS NSIS package prior to 1.3.65 had a bug where it couldn't be uninstalled properly in unattended mode. Therefore the MSI package will not try to uninstall an OpenAFS NSIS package if running unattended. This means that group policy based deployments will fail on machines that have the OpenAFS NSIS package installed.
If you have used a different MSI package to install OpenAFS and wish to upgrade it you can author rows into the 'Upgrade' table as described in the Platform SDK.
When performing an upgrade with msiexec.exe execute the MSI with the repair options "vomus".