ENVIRONMENT * Physical machine * Windows 7 Pro 64 bits with latest Windows update patches I wasn't able to test against Wine on Linux, because of bug 1382592. I managed to get 6 nightlies installed at the same time, by changing the installation location. Only one can run at a time. Uninstalling the right app was easy, because Windows' "Programs and Features" displays the arch and the locale. TESTED SCENARIOS 1. Install a previous nightly build from a day before and force an update (by going to Help > About Nightly) a. en-US => OK, got a partial update b. fr => OK c. es-ES => OK 2. Install the latest nightly, publish a new nightly and force update: 2.1 Before partials are uploaded a. en-US, installed via stub-installer => OK, got a complete update b. fr => OK c. es-ES => OK 2.2 After partials are uploaded a. en-US => OK, got a partial update b. fr => OK c. es-ES => OK 3. Install a previous nightly from 3 days ago before and force an update a. fr => OK, got a partial update I think both en-US and l10n locale behave like we expect. Let's proceed!