If the theme is a bonus theme that allows multiple OS-styles, or the .theme file has nothing that can discern the version of Windows it was targeted at (e.g.: is a Windows 7-8.1 .theme from Microsoft's DLC website), there should be a page before ISO/installation select that allows the user to pick from a list of possible OS-styles, before continuing.
For .theme files, the program should automatically check if the .theme is inside of an existing Windows installation - if this is the case, and all the necessary files exist for installation selection, however skip both this page, and the ISO/installation selection page (the source will be the installation the .theme rests within).
If the theme is a bonus theme that allows multiple OS-styles, or the .theme file has nothing that can discern the version of Windows it was targeted at (e.g.: is a Windows 7-8.1 .theme from Microsoft's DLC website), there should be a page before ISO/installation select that allows the user to pick from a list of possible OS-styles, before continuing.
For .theme files, the program should automatically check if the .theme is inside of an existing Windows installation - if this is the case, and all the necessary files exist for installation selection, however skip both this page, and the ISO/installation selection page (the source will be the installation the .theme rests within).