I know these pages by heard by now I found the problem. But it was not in my config.xml file. When I start the setup manually I'm presented a language selection dialog first (with only English and French as options) before the actual setup dialog is presented. In the root folder there are also 2 folders ProofMUI.en-us and ProofMUI.fr-fr. There isn't an option to set the setup-dialog-language in the config.xml file, but when I remove the fr-fr-folder....setup will continue and start the installation (many thanks to MS for NOT documenting the use of those MUI folders. *sigh*) But now up to the next undocumented problem: the installation starts and when the progress bar is at about 10 or 15% it presents the following error: "setup cannot find proofkit.ww\proof.ar\proof.cab", with an "file open" dialog. If I point the installer to the ...\proof.ar\proof.cab file it gives me the error "This folder can't be used". Nice Also If I point it to a copy (!) of the installation files on a different location it gives the exact same error. See attached screenshots Any help on this is greatly appreciated. )