Not the first GTA in thta series which requires WMP... AFAIK, only way to fix it is re-install and do not remove WMP, also as sidenote GTA`s have issues with N edition Windows builds, which are MS official,,,
Use newer Dism, from Windows 8.1 ADK http://www.microsoft.com/en-us/download/details.aspx?id=39982 Not WinToolkit bug, but Dism incoompatibility issue...
Such tool already exists, it also allows you to keep your Installers always up-to-date. http://ketarin.canneverbe.com/ Also Windows Post Install wizard should be able to work as standalone: http://www.wpiw.net/
AFAIK, WinToolkit does that "automatically" and mounts Def user hive and applies it to that, instead of Current User hive (Which of course does not exists, yet...)
There is minor bug present, it removes first backslash from destination path if destination is UNC path For example \\Server\Directory\Directorybecomes to \Server\Directory\Directory
I dont joke, but if you edit someone elses picture and sell it as yours, then it is copyright violation. And please remember MS doesnt sell you operating system, he is only selling you right to use it. http://www.microsoft.com/en-us/legal/intellectualproperty/UseTerms/default.aspx And trying to use someone elses creation and hard work to stamp your own "label" to it and sell it as your own creation makes things even worse... Lego doesnt earn anything with hes software (WinToolkit is free, as you probably noticed already), and you are pretty much trying to steal the only thing he gets - credit. Exactly...
I read the problem, but you didnt specify which particular Chip has that issue...hence I cannot try to reproduce it, if you dont give me any info... Asmedia 1.16.15.0 works for sure, as I do use it myself to install my Desktop powerhouse...