I have been having a problem with file types in my Basic MSI installation. my installer registers a file type of "ccfile" but in addition to the required key for this: "HKLM\Software\classes\ccfile\shell\Open\command" There is an undocumented key created: "HKLM\Software\classes\ccfile\shell\Open\command\command"  See the screenshot.  This mystery key is a MULTI_SZ type and contains the text name of the related Feature in the installer.  I can confirm this is coming from the installation process.   Normally I'd be happy living with the mystery, but this key is interfering with other file types which were registered by earlier installers, the one thing they have in common is the feature name.  When a user clicks on the earlier file type, they get a re-installation dialog, like for an advertised install (no, this isn't an advertised install) Does anyone know what this key is or where it comes from?  is it from the Windows installer or installsheild? ... View more