Hi Ivar,
I cannot give you an answer myself but I'm very keen at looking at the thread to see if someone will give you one. I am planning on doing a similar clean intall, Windows 8 Pro 64 bit onto Dell All in One XPS 27. I recently bought this desktop but want to reinstall OS from scratch to get rid off all the junk software associated with Dell factory defualt install.
I suppose you've rang Dell support for advices ?