It is recommended that you remove older versions of Flash
Player (unless they are needed for developer testing) when
deploying the new MSI.
There is a known issue when attempting to uninstall using the
current MSI version 9.0.124.0. It will not completely remove all
entries in the system registry. This will be addressed for a future
release of Flash Player.
You can include the Adobe Flash Player uninstaller in your
deployment process. The uninstaller can be downloaded from here:
http://www.adobe.com/go/tn_14157
In addition, the MSI is only available for deployment via the
Adobe Licensing Center:
http://www.adobe.com/licensing/
Please let me know if you have any further questions.